Preheat oven to 350º F and grease or butter a 12 inch cast iron skillet if needed.
Make Custard In a large mixing bowl whisk together 6 eggs, 1 cup whole milk, 1 teaspoon dijon mustard, Salt and pepper until combined. Add in 2 cups ham and 1 1/2 cups sharp cheddar cheese, mix until incorporated.
Prepare Casserole Tear 6 large croissants into thirds and place into the bottom of the prepared cast iron skillet. Pour the custard mixture over the croissants and press down into the egg mixture. Allow to rest and absorb egg mixture while the oven heats up.
Bake the casserole for 25-30 minutes until the edges are golden brown and crisp and the center is no longer jiggly. The cheese will be golden and melted.
Rest the breakfast casserole for at least 5 minutes before serving.
Notes
Nutrition facts are just an estimate of the ingredients listed and are provided as a courtesy
Store any leftovers in an airtight container in the refrigerator for 2-3 days.