My Egg, Vegetable and Croissant Breakfast Casserole is an easy to prepare breakfast for a crowd. This recipe was inspired by my high school classmate Kai who gave me the idea to use croissants and Manchego cheese. These ingredients contributed a luxurious texture and flavor to the casserole. Kai’s version, which includes heavy cream, results in a rich and delicious egg custard. I’ve lightened Kai’s recipe up a bit by omitting the cream however the recipe still requires all 9 eggs. I attempted using fewer eggs but the croissants soaked up the egg mixture and begged for more.
While this casserole does require up to an hour to bake and about 10 minutes to set after, you can prepare much of this dish in advance and serve it to the family on a weekday morning. The onions, mushrooms and protein can be cooked, cooled and then stored in the refrigerator until you are ready to assemble the casserole. The eggs can be whisked with all of the wet and dry ingredient however I prefer to leave out the milk. Storing the egg mixture, without the milk, is easier than finding a container large enough for the eggs and 3 cups of milk. I cover the toasted croissants in the baking dish with aluminum foil and leave it on the counter overnight until I’m ready to assemble the casserole in the morning. If you don’t have an hour to spare in the morning, you can also bake it the night before and reheat it. This casserole makes a great leftover and heats up well either in the microwave or oven.
Serving size: 10-12
- 4 large or 6 small croissants, toasted
- 4-6 tablespoons of olive oil
- ½ medium yellow onion, sliced very thin
- 10 -12 white mushrooms, sliced
- 9 eggs
- ¼ teaspoon freshly ground nutmeg
- ½ teaspoon dry mustard (I prefer Colman’s Dry Mustard Powder)
- 1 teaspoon Worcestershire sauce
- ½ teaspoon Tabasco sauce
- ½ teaspoon Kosher salt
- ¼ teaspoon black pepper
- 3 cups whole milk
- 8 ounces of vegetarian sausage links, browned (Of course you can substitute cooked chopped chicken apple sausage, chopped ham or cooked chopped bacon however I prefer the vegetarian sausages.)
- 2 cups of chopped broccoli
- ½ cup grated English cheddar & ½ cup grated Gruyere OR 1 cup grated Manchego cheese
Preheat oven to 350F
In a sauté pan over medium heat, sauté the thinly sliced onion with about 1 – 2 tablespoons of olive oil. Check on the onion frequently and toss them occasionally until they are golden, fragrant and caramelized. This can take from 15 minutes to 25 minutes depending on how thinly the onions are sliced. Once caramelized, remove the onion from the pan and allow to cool.
While the onion is cooking, cut the croissants in half lengthwise and toast under a 400F broiler, cut side up. I recommend using a kitchen timer set for 5 minutes to start and check frequently.
Butter a 9 x 13 inch glass baking dish.
Tear up the croissants into large pieces and line the bottom of the baking dish. You will have a few pieces of croissant left over. Set the extra croissant pieces aside.
Add another 1 – 2 tablespoons of olive oil to sauté pan used to caramelize the onions. Add the sliced mushrooms and sauté for about 5 minutes. Season the mushrooms with a little salt and pepper. Set aside to cool.
Steam the broccoli in a glass bowl filled with a 2-3 tablespoons of water in the microwave for about 1 minute. The broccoli should be slightly tender but still firm. Remove from excess water, rough chop and set aside to cool. If you are using frozen broccoli, remove any extra moisture after microwaving.
Brown the vegetarian sausage. Chop and allow to cool.
Spread the browned vegetarian sausage slices over the layer of croissants. Next spread the cooled caramelized onion, broccoli, mushrooms and cheese. Top with any remaining croissant pieces.
In a medium size bowl, whisk 9 eggs together. Add nutmeg, dried mustard, Worcestershire sauce, Tabasco sauce, milk, salt and pepper. Whisk to combine. Pour the egg mixture over the croissant and vegetables. Gently press down on all the ingredients with a spatula to ensure everything is moistened and mostly covered by the egg mixture.
Bake in a preheated 350F oven on the middle rack for about 50-60 minutes. The casserole is done when a knife inserted comes out clean and there is no liquid running. If the top starts to get too brown, cover with aluminum foil.
Remove from the oven, loosely cover with aluminum foil and allow it to sit for about 10 minutes before serving.