I grease a 9-by-13-inch baking dish and scatter the croissant pieces inside.

I layer the ham and cheese over the top.

I whisk the eggs, milk, mustard, salt, and pepper in a bowl, then pour the mixture evenly over everything.

I press the croissants down gently so they soak up the custard. After 10 minutes, I bake at 350°F for 35 to 40 minutes, until the center is set.