Step 1

Preheat Oven to 400˚F with the rack in the center. Butter a 9x13 casserole dish. Arrange trimmed asparagus in prepared casserole dish, packing it down for a fairly flat and even surface.

Step 2

Place a saucepan over medium heat. Melt in 3 Tbsp butter then add 2 1/2 Tbsp flour and whisk constantly for 3 minutes or until butter just starts to turn golden in color. Whisk in 2 cups half and half, 2 tsp garlic salt and 1/4 tsp black pepper. Whisk until sauce just starts to thicken then remove from heat. Sprinkle in 1/2 cup parmesan and whisk until cheese is melted and incorporated.

Step 3

Pour sauce evenly over the asparagus, leaving about 1" space on the long sides of the casserole dish. Bake uncovered at 400˚F for 15-18 minutes (depending on thickness of asparagus), or until asparagus reaches desired tenderness.

Step 4

While the casserole is baking, make the topping: in a small mixing bowl, melt 1 Tbsp butter. Mix in 1/2 cup bread crumbs, stirring until evenly moistened, then stir in 1/2 cup remaining parmesan cheese. Halfway through baking, sprinkle the bread crumb topping evenly over the casserole then return it to the oven to finish baking.

Step 5

When asparagus has reached desired doneness, set oven to broil for 2-3 minutes or until bread crumbs are golden brown. Remove from oven and serve.