brunch casserole with gruyere cheese and caramelized onions
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Brunch Casserole with Gruyere Cheese and Caramelized Onions

Brunch Casserole with Gruyere Cheese and Caramelized Onions is amazing as a main dish or a side dish! I love making this for special occasions, the gruyere cheese makes it feel extra fancy. It’s a great Mother’s Day breakfast casserole, Christmas breakfast casserole, and Easter breakfast casserole!

Ingredients for Brunch Casserole with Gruyere Cheese and Caramelized Onions

  • Challah or Brioche Bread: Challah bread and brioche bread are actually made very differently, specifically, challah is made without any butter, and brioche is made with a lot of butter. However, they are both flaky and sturdy, which made them great candidates for breakfast casserole with bread.
  • Sweet Onion & Shallot: For this breakfast casserole we caramelize these together to add some balance to the savory flavors in this dish. The sweet onion will add some sweetness which works perfectly with the mushrooms and gruyere.
  • Mushrooms: Mushrooms add some extra flavor to this vegetarian casserole and give it a little bite. It’s okay to omit these, but I love mushrooms here.
  • Eggs & Egg Yolks: It wouldn’t be a breakfast casserole without eggs!
  • Whole Milk & Heavy Cream: I’ve tested this recipe with just milk, and it still tastes amazing, so if you don’t have cream, that’s fine. I like the extra richness that comes from using both milk and cream if I have it on hand.
  • Gruyere: Gruyere is a rich and savory cheese. It stands up well to the caramelized onion and shallot because gruyere is packed with flavor.
  • Butter, salt, pepper: A mix of some simple seasonings to bring out the flavors.
  • Thyme: Fresh thyme adds fragrance and earthiness.

How to make Brunch Casserole with Gruyere Cheese and Caramelized Onions

  1. Adjust rack to the middle position, then preheat the oven.
  2. Caramelize the onions & shallot: Heat a non-stick saute pan over low heat. Add sliced onion, shallots, some butter, and some coarse salt. Saute on low heat stirring frequently until onions caramelize. Once onions and shallots are caramelized, spoon them from the pan into a mixing bowl.
  3. Toast the bread: Place the cubes of bread on a baking sheet and toast in the oven until lightly browned.
  4. Saute the mushrooms: Turn the heat on the onion pan up to medium and add some butter, sliced mushrooms, and some salt. Saute over medium heat until mushrooms are browned on both sides. Spoon the mushrooms from the pan into the large mixing bowl with the onions and shallots.
  5. Egg mix: Wait to do this until the mushrooms are done cooking and out of the pan. They need a few minutes to cool so you don’t cook the eggs. In a medium mixing bowl, mix together the eggs, egg yolks, whole milk, heavy cream, coarsely ground pepper, and fresh thyme leaves
  6. Put it all together: In the large bowl with mushrooms and onions, add toasted bread cubes and stir together until mushrooms and onions are evenly distributed. Add in ounces grated gruyere and stir together. Pour the egg mixture over the bread and stir gently until the egg is distributed. Take care to not mash up the bread.
  7. Bake: In a 9×13 pan, spoon bread mixture into the pan and top with the remaining 1 ounce of Gruyere cheese. Bake at 350°F until the egg is set and the cheese is browned, about 25 to 30 minutes.

Techniques for a Perfect Brunch Casserole

  • Challah bread or brioche bread is light enough to soak up the egg. 
  • Caramelizing the onions brings out their sweetness which balances all the savory components. 
  • Sweet and salty Gruyere cheese adds a delicious and complex flavor.

If you’re looking for a sweet dish to pair with this savory casserole, try our Custard French Toast with Strawberry Lemon Glaze.

Yield: 4 Large Servings

Brunch Casserole with Gruyere Cheese and Caramelized Onions

brunch casserole with gruyere cheese and caramelized onions

This rich and savory brunch casserole is perfect as a side for a large group, or a main for about 4 people.

Prep Time 10 minutes
Cook Time 30 minutes
Total Time 40 minutes

Ingredients

  • 1 loaf challah or brioche bread, sliced into 1 inch cubes
  • 1 sweet onion, remove ends and slice thinly
  • 1 shallot, remove ends and slice thinly
  • 8 ounces mushrooms, sliced
  • 6 eggs
  • 2 egg yolks
  • 1/2 cup whole milk
  • 1/2 cup heavy cream
  • 7 ounces gruyere, grated and divided into 5 ounces and 2 ounce
  • 4 tablespoons butter
  • 1 teaspoon coarse salt
  • 1/2 teaspoon pepper
  • 1 teaspoon fresh thyme leaves

Instructions

    1. Adjust rack to the middle position, then preheat the oven to 350°F.
    2. Caramelize the onions & shallot: Heat a non-stick saute pan over low heat. Add sliced onion, shallots, 2 tablespoons butter, 1/2 teaspoon coarse salt. Saute on low heat stirring frequently until onions caramelize, about 30 minutes. Once onions and shallots are caramelized, spoon them from the pan into a mixing bowl.
    3. Toast the bread: Place the cubes of bread on a baking sheet and toast in the oven until lightly browned, about 5 minutes.
    4. Saute the mushrooms: Turn the heat on the onion pan up to medium and add 2 tablespoons butter, sliced mushrooms, 1/2 teaspoon salt. Saute over medium heat until mushrooms are browned on both sides. Spoon the mushrooms from the pan into the large mixing bowl with the onions and shallots.
    5. Egg mix: Wait to do this until the mushrooms are done cooking and out of the pan. They need a few minutes to cool so you don’t cook the eggs. In a medium mixing bowl, mix together 6 eggs, 2 egg yolks, 1/2 cup whole milk, 1/2 cup heavy cream, 1/2 teaspoon coarsely ground pepper, and 1 teaspoon fresh thyme leaves
    6. Put it all together: In the large bowl with mushrooms and onions, add toasted bread cubes and stir together until mushrooms and onions are evenly distributed. Add in ounces of grated gruyere and stir together. Pour the egg mixture over the bread and stir gently until the egg is distributed. Take care to not mash up the bread.
    7. Bake: In a 9x13 inch pan, spoon the bread mixture into the pan and top with the remaining 1 ounce of Gruyere cheese. Bake at 350°F until the egg is set and the cheese is browned, for about 25 to 30 minutes.

Nutrition Information:

Yield:

4

Serving Size:

1

Amount Per Serving: Calories: 559Total Fat: 41gSaturated Fat: 23gTrans Fat: 1gUnsaturated Fat: 16gCholesterol: 485mgSodium: 971mgCarbohydrates: 27gFiber: 3gSugar: 11gProtein: 22g

Nutrition information isn’t always accurate.

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