Preheat the oven to 400 degrees F (200 degrees C).
Arrange asparagus spears in a shallow baking dish.
Whisk together half-and-half, cornstarch, Italian seasoning, ground mustard, red pepper flakes, mozzarella cheese, and Parmesan cheese. Pour mixture over asparagus and swirl the dish so that liquid coats the bottom of the dish.
Bake in the preheated oven until asparagus is soft and cheese sauce starts to bubble, about 15 minutes. Remove from oven and let sit for 5 minutes before serving.