While you prepare your other components, preheat your oven to 350°F and lightly grease a 9x13 inch baking dish (or similar size that fits your crepes snugly). If you're making crepes from scratch, prepare them according to your recipe and set aside. Have all your crepes ready and at room temperature before assembly—this makes them easier to work with and less likely to tear.

Trim the tough woody ends off the asparagus spears (usually about 1-2 inches from the bottom). Microwave the asparagus with 1 tablespoon of water for 3 minutes until they're tender-crisp but still have a slight bite to them. This partial cooking ensures they'll be perfectly tender after baking and won't release excess moisture into your sauce. Drain and set aside.

Lay out each crepe and layer one slice of ham, then one slice of swiss cheese, then 3 blanched asparagus spears along one edge. Roll the crepe tightly around the filling and place seam-side down in your prepared baking dish. I like to arrange them snugly so they support each other while baking and the cheese gets nice and melty. Repeat with remaining crepes until the dish is full.

Place the baking dish in your preheated 350°F oven and bake for 30 minutes. The crepes should be heated through and the cheese will begin to melt into the ham. While they bake, you'll prepare the sauce.

While the crepes are baking, combine the bearnaise mix, sour cream, and 3 tablespoons of water in a microwave-safe bowl, stirring well to create a smooth mixture with no lumps. Microwave on high for 3-4 minutes, stirring every minute to ensure even heating and a silky consistency. The sauce will thicken as it heats. I prefer using Knorr bearnaise mix because it creates a more stable, creamy sauce that doesn't break.

Remove the crepes from the oven and pour the warm bearnaise sauce generously over the top, allowing it to cascade between the rolls and soak in. Serve immediately while everything is hot and the cheese is at its creamiest. The asparagus and ham will have absorbed the flavors while baking, and the sauce will tie everything together beautifully.