Prep the Croissants: Roughly chop croissants into 1-inch pieces.
Cook the Bacon: Cut bacon into bite-sized pieces and cook in a large skillet over medium heat until crispy (about 8–10 minutes).
Make the Egg Custard: In a big mixing bowl, whisk together eggs, milk, cream, Dijon mustard, salt, and black pepper.
Assemble the Casserole: Grease a 9×13 baking dish with butter or nonstick spray. Scatter the croissant pieces evenly in the pan. Pour the egg mixture over the top.
Bake: Bake at 350°F (175°C) uncovered for 40–45 minutes.
Rest and Serve: Let it cool for 5–10 minutes before slicing.
