Rich Ham and Cheese Croissant Breakfast Bake

Here is my favorite ham and cheese croissant breakfast bake, with buttery croissants soaked in a creamy custard, layered with gruyere cheese and savory ham, and topped with caramelized onions and fresh herbs.

This breakfast bake is what I make when I want to feel like we’re having brunch at a fancy hotel but without leaving the house. It’s also perfect for using up day-old croissants, and you can assemble it the night before and just pop it in the oven in the morning.

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What Kind of Croissants Should I Use?

For this breakfast bake, you’ll want to use day-old or slightly stale croissants if you can find them – they’ll soak up the egg mixture better without getting too soggy. Fresh croissants from your local bakery are always a great choice, but honestly, the ones from the grocery store bakery section work just fine too. If you only have fresh croissants on hand, you can leave them out on the counter overnight or pop them in a low oven for about 10 minutes to dry them out a bit. The size of your croissants matters less than you’d think, so don’t stress if yours are smaller or larger than average – just adjust the number you use to fill your baking dish.

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Options for Substitutions

This breakfast bake is pretty forgiving when it comes to swaps, so here are some options if you need them:

• Croissants: Croissants are really what make this dish special with their buttery, flaky texture, so I’d recommend sticking with them if possible. If you absolutely need to substitute, try brioche or challah bread, but keep in mind the texture won’t be quite the same.
• Gruyere cheese: Swiss cheese is the closest match and works great here. You can also use sharp white cheddar or fontina for a different flavor profile.
• Ham: Cooked bacon, turkey, or Canadian bacon all work well. If using bacon, cook it first and crumble it before adding to the dish.
• Half and half: You can use whole milk for a lighter version, or mix equal parts heavy cream and milk if you don’t have half and half on hand.
• Fresh herbs: If you don’t have fresh thyme and sage, use 1 teaspoon dried thyme and 2 teaspoons dried sage instead. Just remember that dried herbs are more concentrated than fresh.
• Dijon and whole grain mustard: If you only have one type of mustard, just use 2 tablespoons of whichever you have. Yellow mustard can work in a pinch, though the flavor will be milder.

Watch Out for These Mistakes While Baking

The biggest mistake with this breakfast bake is not toasting or drying out your croissants before assembling – fresh, soft croissants will become mushy instead of maintaining their flaky texture, so let them sit out overnight or toast them lightly in the oven first.

Another common error is pouring all the custard mixture at once, which can cause it to pool at the bottom rather than distribute evenly – instead, pour half the mixture over the croissants, let it soak for a few minutes, then add the rest.

Don’t skip sautéing the onions until they’re soft and golden before adding the herbs, as raw onions will release too much moisture during baking and create a watery casserole.

Finally, resist the urge to cut into the bake immediately after removing it from the oven – letting it rest for at least 15 minutes allows the custard to set properly, making it much easier to serve in neat portions.

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What to Serve With Ham and Cheese Croissant Breakfast Bake?

This breakfast bake is pretty filling on its own, so I like to keep the sides simple and fresh. A light arugula or mixed greens salad with a lemon vinaigrette cuts through the richness perfectly, or you could go with fresh fruit like berries, melon, or sliced oranges for a sweet contrast. If you’re feeding a crowd for brunch, consider adding some crispy bacon or breakfast sausage on the side, along with a pitcher of mimosas or fresh-squeezed orange juice. For a more casual morning, a simple cup of coffee and some extra chives sprinkled on top is really all you need to make this feel complete.

Storage Instructions

Make Ahead: This breakfast bake is perfect for prepping the night before. Just assemble everything in your baking dish, cover it tightly with plastic wrap, and stick it in the fridge overnight. In the morning, let it sit on the counter while your oven preheats, then bake as directed.

Store: Leftovers will keep in an airtight container in the fridge for up to 3 days. The croissants will soften a bit more as they sit, but the flavors actually get even better as everything melds together.

Reheat: Warm up individual portions in the microwave for about 1-2 minutes, or reheat the whole dish covered with foil in a 350°F oven for 15-20 minutes. You can also pop a slice in the toaster oven for a few minutes if you want to crisp up the top a bit.

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 5200-5700
• Protein: 170-200 g
• Fat: 340-390 g
• Carbohydrates: 320-370 g

Ingredients

For the croissant base:

• 10 large croissants (day-old for better texture and absorption)
• 6 oz sliced ham (deli counter preferred)
• 2 cups shredded gruyere cheese (freshly shredded for better melting)

For the sautéed onions:

• 2 tbsp fresh sage (or 1 tsp dried sage)
• 1 tbsp fresh thyme
• 1 yellow onion (thinly sliced into half-moons)
• 4 tbsp unsalted butter (I use Kerrygold)

For the custard:

• 1.5 tsp kosher salt
• 6 eggs (room temperature for smoother custard)
• 0.5 tsp ground black pepper
• 2.5 cups half and half
• 1 tbsp whole grain mustard
• 1/8 tsp freshly grated nutmeg (for warm spice notes)
• 1 tbsp Dijon mustard

For serving (optional):

• minced chives (optional, adds fresh onion flavor)
• hollandaise sauce (optional but recommended for richness)

Step 1: Prepare the Custard Base

• 6 eggs
• 2.5 cups half and half
• 1 tbsp whole grain mustard
• 1 tbsp Dijon mustard
• 1.5 tsp kosher salt
• 0.5 tsp ground black pepper
• 1/8 tsp freshly grated nutmeg

In a large bowl, whisk together the eggs, half and half, whole grain mustard, Dijon mustard, kosher salt, black pepper, and freshly grated nutmeg until smooth and well combined.

Set aside at room temperature while you prepare the other components.

This custard is the foundation of the bake, and whisking it early ensures all ingredients are fully incorporated before it needs to soak into the croissants.

Step 2: Caramelize the Onions with Herbs

• 4 tbsp unsalted butter
• 1 yellow onion
• 2 tbsp fresh sage
• 1 tbsp fresh thyme

Melt the unsalted butter in a large skillet over medium heat.

Add the thinly sliced yellow onion and cook for 2-3 minutes until softened and translucent.

Then add the fresh sage and fresh thyme, cooking for another 2-3 minutes to release the aromatic oils and infuse the butter with herbal flavor.

I like to let the herbs bloom in the hot butter just long enough to smell their perfume—it transforms the whole dish.

Remove from heat and let cool slightly.

Step 3: Toast the Croissants

• 10 large croissants

Tear the day-old croissants into large bite-sized pieces and spread them on a baking sheet in a single layer.

Place in a 250°F oven for about 40 minutes, stirring occasionally, until they’re lightly toasted and slightly dried out.

Day-old croissants are crucial here because they’re sturdy enough to soak up the custard without falling apart, and the light toasting helps them hold their structure even better during the bake.

Step 4: Assemble the Bake

• toasted croissants from Step 3
• 6 oz sliced ham
• 2 cups shredded gruyere cheese
• caramelized onion mixture from Step 2

Grease a 9×13 inch baking pan with butter.

Layer half of the toasted croissants from Step 3 on the bottom of the pan, then distribute half of the sliced ham and half of the shredded gruyere cheese over them.

Scatter half of the caramelized onion mixture from Step 2 (including the herbed butter) over the cheese.

Top with the remaining croissants, then the rest of the ham, cheese, and caramelized onions.

This layering ensures even distribution of flavors and prevents the ham and cheese from settling to the bottom.

Step 5: Soak and Prepare for Baking

• custard base from Step 1

Pour the custard base from Step 1 evenly over the assembled layers, then gently press down on the croissants with the back of a spatula to help them absorb the liquid.

Let the bake sit at room temperature for about 30 minutes, allowing the croissants to soak up the custard—this creates a creamy, cohesive texture rather than dry pockets.

While soaking, preheat your oven to 350°F.

Step 6: Bake and Finish

• hollandaise sauce
• minced chives

Bake the assembled bake in the preheated 350°F oven for 40-45 minutes, until the top is golden brown and a knife inserted into the center comes out clean with no uncooked custard.

Let it rest for 5 minutes before serving.

If desired, drizzle with hollandaise sauce and garnish with minced chives for extra richness and a fresh onion brightness that cuts through the richness of the ham and cheese.

Rich Ham and Cheese Croissant Breakfast Bake

Delicious Rich Ham and Cheese Croissant Breakfast Bake recipe with step-by-step instructions.

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Prep Time 35 minutes mins

Cook Time 1 hour hr 10 minutes mins

Total Time 1 hour hr 45 minutes mins

Servings 8 servings

Calories 5450 kcal

Ingredients

  

For the croissant base:

• 10 large croissants (day-old for better texture and absorption)
• 6 oz sliced ham (deli counter preferred)
• 2 cups shredded gruyere cheese (freshly shredded for better melting)

For the sautéed onions:

• 2 tbsp fresh sage (or 1 tsp dried sage)
• 1 tbsp fresh thyme
• 1 yellow onion (thinly sliced into half-moons)
• 4 tbsp unsalted butter (I use Kerrygold)

For the custard:

• 1.5 tsp kosher salt
• 6 eggs (room temperature for smoother custard)
• 0.5 tsp ground black pepper
• 2.5 cups half and half
• 1 tbsp whole grain mustard
• 1/8 tsp freshly grated nutmeg (for warm spice notes)
• 1 tbsp Dijon mustard

For serving (optional):

• minced chives (optional, adds fresh onion flavor)
• hollandaise sauce (optional but recommended for richness)

Instructions

 

• In a large bowl, whisk together the eggs, half and half, whole grain mustard, Dijon mustard, kosher salt, black pepper, and freshly grated nutmeg until smooth and well combined. Set aside at room temperature while you prepare the other components. This custard is the foundation of the bake, and whisking it early ensures all ingredients are fully incorporated before it needs to soak into the croissants.
• Melt the unsalted butter in a large skillet over medium heat. Add the thinly sliced yellow onion and cook for 2-3 minutes until softened and translucent. Then add the fresh sage and fresh thyme, cooking for another 2-3 minutes to release the aromatic oils and infuse the butter with herbal flavor. I like to let the herbs bloom in the hot butter just long enough to smell their perfume—it transforms the whole dish. Remove from heat and let cool slightly.
• Tear the day-old croissants into large bite-sized pieces and spread them on a baking sheet in a single layer. Place in a 250°F oven for about 40 minutes, stirring occasionally, until they're lightly toasted and slightly dried out. Day-old croissants are crucial here because they're sturdy enough to soak up the custard without falling apart, and the light toasting helps them hold their structure even better during the bake.
• Grease a 9x13 inch baking pan with butter. Layer half of the toasted croissants from Step 3 on the bottom of the pan, then distribute half of the sliced ham and half of the shredded gruyere cheese over them. Scatter half of the caramelized onion mixture from Step 2 (including the herbed butter) over the cheese. Top with the remaining croissants, then the rest of the ham, cheese, and caramelized onions. This layering ensures even distribution of flavors and prevents the ham and cheese from settling to the bottom.
• Pour the custard base from Step 1 evenly over the assembled layers, then gently press down on the croissants with the back of a spatula to help them absorb the liquid. Let the bake sit at room temperature for about 30 minutes, allowing the croissants to soak up the custard—this creates a creamy, cohesive texture rather than dry pockets. While soaking, preheat your oven to 350°F.
• Bake the assembled bake in the preheated 350°F oven for 40-45 minutes, until the top is golden brown and a knife inserted into the center comes out clean with no uncooked custard. Let it rest for 5 minutes before serving. If desired, drizzle with hollandaise sauce and garnish with minced chives for extra richness and a fresh onion brightness that cuts through the richness of the ham and cheese.