Looking for a delicious overnight breakfast casserole recipe for your holiday celebrations? This savory Croissant Breakfast Casserole is full of ham, mushrooms, and gruyere cheese for a breakfast that will satisfy all of your guests.
8ouncessliced fresh mushroomssuch as crimini or shiitake
1largeleeksliced
1mediumoniondiced
1teaspoonfine sea saltdivided
3-4clovesgarlicminced
2tablespoonswhole-grain mustard
1tablespoonsherry vinegaroptional
8largeeggs
2cupswhole milk
6-8ouncesdiced smoked ham
6ouncesgrated Gruyere cheese
2ouncesfreshly grated parmesan cheese
½teaspoonblack pepper
12ouncescroissantscut or torn into 1-inch pieces
Instructions
In medium pan, melt the butter over medium heat. Add the mushrooms, leeks, and onion with ¼ teaspoon of the salt. Saute for about 10 minutes. When the mushrooms and onions are soft and caramelized, add the garlic, mustard, and sherry vinegar and cook for 1 additional minute. Set aside to cool.
In a large bowl, whisk the eggs and milk until thoroughly combined. Add the cooled mushroom mixture, ham, cheeses, and black pepper, and remaining ¾ teaspoon of salt. Gently fold in the croissant pieces.
Generously butter a 9x13-inch baking dish. Add the casserole mixture to the pan. Cover and refrigerate overnight.
In the morning, preheat the oven to 375ºF. Bake the casserole for 1 hour, or until the top is golden, the edges are crispy, and the center is set.