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Overnight Ham and Gruyère Croissant Breakfast Casserole

Close-up of a cheesy Croissant Breakfast Casserole slice showing flaky layers, ham chunks, and melted white sauce.
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Prepare this make-ahead breakfast bake the night before for an easy, indulgent weekend brunch or holiday morning meal. Flaky croissants soak up a creamy custard with savory ham and rich Gruyère cheese.

Ingredients

Scale
  • 8 large croissants, torn into 1-inch pieces
  • 1 cup diced fully cooked ham
  • 1 cup shredded Gruyère cheese
  • 1 cup shredded sharp cheddar cheese
  • 6 large eggs
  • 2 cups whole milk
  • 1 teaspoon Dijon mustard
  • 1/2 teaspoon garlic powder
  • 1/2 teaspoon salt
  • 1/4 teaspoon black pepper
  • 1 tablespoon butter, melted (for greasing)

Instructions

  1. Lightly grease a 9×13 inch baking dish with melted butter.
  2. Arrange half of the torn croissants evenly in the bottom of the prepared dish.
  3. Sprinkle the diced ham and half of the Gruyère and cheddar cheese over the croissants.
  4. Top with the remaining croissant pieces, followed by the rest of the cheese.
  5. In a large bowl, whisk together the eggs, whole milk, Dijon mustard, garlic powder, salt, and pepper until fully combined.
  6. Slowly pour the egg mixture evenly over the croissants and cheese in the baking dish, pressing down gently to ensure all pieces absorb the liquid.
  7. Cover the baking dish tightly with plastic wrap. Refrigerate for at least 8 hours, or preferably overnight.
  8. When ready to bake, preheat your oven to 350°F (175°C). Remove the plastic wrap.
  9. Bake uncovered for 40 to 50 minutes, or until the casserole is puffed, golden brown on top, and the center is set (no liquid remains when pierced with a knife).
  10. Let the casserole rest for 10 minutes before slicing and serving.

Notes

  • For a richer flavor, use half-and-half instead of whole milk in the custard mixture.
  • If you need to bake this immediately, let the assembled casserole sit at room temperature for 30 minutes before baking, though the texture will be less strata-like.
  • You can substitute Gruyère with Swiss cheese or sharp white cheddar for a similar flavor profile.

Nutrition

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