Preheat your oven to 350°F (175°C) to ensure it's hot and ready for baking. Meanwhile, lightly grease a 9x13 inch baking dish with butter or nonstick spray to prevent the casserole from sticking.

Heat a skillet over medium-high heat. Add the ground pork breakfast sausage, diced red bell pepper, and chopped onion. Break up the sausage with a spatula as it cooks. Continue cooking until the sausage is no longer pink and the vegetables have softened. Drain off any excess grease from the skillet to keep the casserole from being greasy.

Add the chopped fresh spinach to the skillet with the cooked sausage mixture. Cook for an additional 1-2 minutes until the spinach is wilted. Remove the skillet from the heat and let the mixture cool slightly—this helps prevent the eggs from scrambling when mixed in later.

In a large mixing bowl, whisk together the eggs, kosher salt, ground black pepper, and whole milk or plain coconut milk until well combined. Stir in the frozen hash brown potatoes and 1 cup of finely shredded sharp cheddar or nondairy cheese. This will make the mixture rich and creamy before you add the cooked sausage and vegetable mixture.

Add the cooled sausage, onion, red pepper, and spinach mixture from Step 3 into the bowl with the egg mixture. Stir well until fully incorporated. Pour the combined mixture into your prepared baking dish and spread evenly. Sprinkle extra cheese over the top for a delicious melty crust—I always like to add a little extra cheese at this stage for a golden, bubbly topping.

Place the assembled casserole in the preheated oven and bake, uncovered, for 25-30 minutes until the eggs are set and the top is golden. Let the casserole cool slightly before slicing and serving—this helps the pieces hold together neatly. For extra flavor, I sometimes serve it with a dash of hot sauce on the side.