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Ham and Cheese Croissant Casserole

Ham and cheese croissant casserole with flaky torn croissants baked in a rich, savory egg and gruyère custard. The tops turn deeply golden and caramelized while gruyère bubbles throughout for an easy brunch casserole bake.
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Prep Time 15 minutes
Cook Time 40 minutes
soaking/resting 30 minutes
Total Time 1 hour 25 minutes
Servings: 8 servings
Course: Breakfast
Cuisine: French-American
Calories: 640
Ingredients Equipment Method Notes

Ingredients
  

Croissant base
  • 6 croissants Torn into large pieces.
  • 1.5 cup diced ham
  • 1.5 cup Gruyère or Swiss cheese Shredded, divided (use 1 cup first, remaining for topping).
Custard
  • 6 eggs
  • 2 cup whole milk
  • 0.5 cup heavy cream
  • 1 tbsp Dijon mustard
  • 1 tsp garlic powder
  • 0.25 tsp salt To taste.
  • 0.25 tsp black pepper To taste.
  • 1 fresh thyme For garnish.

Equipment

  • 1 sheet pan

Method
 

Assemble
  1. Grease a 9x13 dish and arrange the torn croissant pieces in an even layer. Leave little gaps so the custard can soak in and puff up.
  2. Scatter the diced ham and 1 cup of the shredded gruyère over the croissants. Distribute it so you get ham and cheese bites throughout.
  3. Whisk the eggs, whole milk, heavy cream, Dijon mustard, garlic powder, salt, and black pepper until smooth. Pour the custard over the croissants and press down so the pieces absorb it.
  4. Let the casserole rest for 30 minutes to soak. For make-ahead, cover and refrigerate overnight.
Bake and finish
  1. Heat the oven to 350°F and sprinkle the remaining cheese over the top. This sets you up for a bubbly, browned surface.
  2. Bake at 350°F for 35–40 minutes until the casserole is puffed and deeply golden. You should see gruyère bubbling around the edges.
  3. Garnish with fresh thyme and serve warm. Let it sit briefly so the custard sets and slices cleanly.

Notes

Pro tip: press down firmly right after pouring the custard so every croissant gets saturated, then don’t rush the soak time—30 minutes (or overnight) makes the center set up like a true egg bake. Refrigerate leftovers up to 3 days; reheat in the oven at 325°F until warmed through. Freezing is not recommended because croissants can soften and the custard texture may change. For a lighter option, use low-fat milk and reduce the heavy cream to 1/4 cup while keeping the eggs and cheese the same.