Preheat oven to 325 degrees Fahrenheit
Mix together the eggs, dairy, and spices: Get out a large bowl, and crack the eggs into it. Then pour in the milk and half & half, along with some salt and pepper, and the nutmeg if using. Whisk all of these ingredients together and set aside.
Assemble the casserole: Get out a 3×19 casserole pan and grease it with some spray oil like Pam. Next slice the pieces of bread into 1 inch sized cubes, and toss them into the casserole pan. Then add both the prosciutto and asparagus on top of the bread. Top this off by sprinkling on both the cheddar and parmesan cheese. Finally, pour the egg and dairy mixture over everything.
Place the casserole in the oven and bake for 45 minutes
Take the asparagus & prosciutto breakfast casserole out, and let it sit for 1 minute before cutting and serving. Enjoy!