When I’m asked to make breakfast casseroles for a crowd, my default is usually some variation of a strata. Essentially, a strata is a savory bread casserole, soaked with eggs and layered with cheese and baked to golden brown. It’s a handy, make-ahead dish that’s ready to pop in the oven the next morning, making it a no-brainer for Christmas, Easter or any weekend. Breakfast and brunch casseroles like this are known for their crusty, golden tops and soft, lush interiors. It’s easy to customize the flavors of egg and bread strata to suit your tastes, but you’ll want to give this combo a try. This easy egg strata is filled with bacon, mushrooms and sweet caramelized onions, for an overnight casserole even picky eaters love.
I’ve been eating bread casseroles like this my whole life. They were one of my mother’s favorite ways to feed a crowd during the holidays and never failed to elicit “ooh’s and aah’s” from the diners. This one includes crispy bacon, melty cheese, meaty mushrooms and sweet, jammy caramelized onions and it’s homey enough for family, but fancy enough for company.
An egg bake (baked egg casserole) is primarily eggs with other flavorings such as meats, vegetables and cheeses added. Egg strata is more like a savory bread pudding because one of the main components is bread, which is soaked in an egg/milk custard until its saturated with the egg mixture. It’s then baked, developing a crispy, craggy crust and soft, tender interior. Breakfast strata are sublime.
Ingredients for breakfast strata
- Stale Sourdough or Italian Bread
- Baby Bella or White Button Mushrooms
- Caramelized Onions
- Shredded Mozzarella or Italian Blend Cheese
- Kosher Salt
- White Pepper (can use black pepper)
- Cayenne Pepper
- Dry Mustard
- Dried Thyme
- Onion Powder
Why use stale bread?
It’s important to use sturdy, stale bread for a breakfast strata for the same reason you’ll use stale bread or croutons in traditional stuffing recipes. If you used a soft, fresh loaf, the bread won’t hold it’s texture and turns to mush (not what we’re going for with this brunch casserole). I prefer a crusty bakery-style sourdough or Italian loaf and will either purchase one a few days ahead of time (to allow it time to get stale) or remove the crusts and cut into bite sized cubes in a large bowl to rest on the counter, uncovered, overnight. The second method is my last minute effort to accelerate becoming stale and hasten the recipe.
Even though the easy egg strata is a baked casserole, you’ll want to fry the bacon BEFORE adding it to the breakfast strata, so that you’ve got crispy bits of bacon throughout.
Tips on frying bacon
- Cut the bacon into bite sized pieces before cooking it.
- Use a heavy bottomed skillet, to prevent hot spots and over-crisping
- Heat the pan before adding the bacon, that way it starts to render the fat immediately and crisps quickly.
- Place the lid 3/4 of the way on the pan to lessen splatters or use a splatter screen. (If you’ve ever had hot bacon grease spit from the pan, you know what I mean)
- Transfer cooked bacon with a slotted spoon or kitchen spider to a plate lined with paper towels to soak up excess bacon fat.
- Reserve a one or two teaspoons of the bacon fat to fry the mushrooms. Discard the rest – but don’t put bacon grease down your drain unless you like high plumbing bills.
Cooking the mushrooms before adding them to the strata will bring out their flavors, especially since we cook them in a bit of the rendered bacon grease.
Tips on mushrooms
- Mushrooms contain a lot of water and when cooked over a medium high heat, they’ll release their liquid and shrink considerably. This brunch casserole uses 16 ounces of mushrooms, which may be too many to fit in one pan. I recommend cooking the mushrooms in two or three batches so they can release their liquid and brown.
- Heat the reserved bacon fat over medium high heat before adding the first batch of mushrooms.
- Don’t over-stir. Let them brown for a few minutes before agitating the fungi, then flip them and brown the other side.
A word on caramelized onions
I know it seems unfair that I would use caramelized onions as an “ingredient” for this breakfast strata recipe. After all, getting a good caramelization can take upwards of more than an hour. I’ve got a work-around if you’re in a rush, but read this next section, so you’re good to go next time.
Difference between caramelized & sautéed onions
Caramelized onions are VERY DIFFERENT from sautéed or grilled onions. The slow-caramelization process transforms them from eye-stinging alliums to jammy, sweetness that you can literally eat with a spoon or spread over a cracker. That’s how tender and luscious they are. Sautéed onions are quickly cooked over high heat in a little oil, producing browned onions that still have a little bite. Grilled onions can be made in a skillet or on a grill and are usually cooked just enough to take away the sting, but still have crunch.
Make ahead caramelized onions
I like to make 5 pounds of caramelized onions at one time. That may sound like a lot, however, 5 pounds reduces down to about 2 cups of onions. Divide them into half cup or quarter cup containers and freeze them, so you’ve always got caramelized onions at the ready.
For this recipe, you can use sautéed sliced onions as a substitute, but if you’ve got the time, try my Caramelized Onions recipe and become a convert.
Blending brunch casserole ingredients
- In a large bowl, combine the stale bread cubes, bacon, mushrooms, caramelized onions, shredded cheese and parsley.
- Toss well to combine.
- Spray a casserole dish with vegetable spray and fill it with the bread mixture, making sure that the ingredients are evenly distributed throughout the breakfast strata casserole.
The spices and seasonings in the custard are responsible for flavoring this easy egg strata casserole. The cayenne pepper adds just a hint of heat, so if you like spice, you may want to up the amount to 1/2 teaspoon. The dry mustard is important for a little tanginess and rounds out the flavors so they aren’t flat.
Making custard for the strata
- In a small bowl, combine the eggs, salt, pepper, dry mustard, cayenne, thyme, onion powder and milk.
- Whisk well to combine.
Assembling the strata
- Pour the custard evenly over the entire bread casserole.
- Cover with plastic wrap and refrigerate for at least a few hours or overnight.
How long does strata need to soak?
You’ll want to soak the egg strata for a minimum of 2 hours. The bread needs to soak up the custard and evenly distribute the flavors. As the casserole rests, the egg custard is absorbed by the cubed bread, assuring that there are no dry pieces in the strata. If you’ve got the time, an overnight rest is optimal.
How long can it rest before baking?
You can easily assemble this bread casserole 2-3 days in advance and keep it refrigerated. So if it’s the holidays and you’re trying to get a thousand things done at once… this breakfast casserole is definitely a great make-ahead item.
Tips on baking the casserole
- Before baking, remove the brunch casserole from the refrigerator and let rest at room temperature for 30-45 minutes before cooking. This takes the chill off the ingredients and starts the cooking process sooner once it goes into the oven.
- Sprinkle extra cheese over the casserole (if desired — and who wouldn’t desire that?) and bake until the topping is golden and crusty and the egg custard is cooked through.
- Let the bread casserole rest for 5-10 minutes before serving.
Can you freeze the brunch casserole?
Yes. You’ll want to bake the strata first, then let it come to room temperature. Cover tightly with foil and freeze for up to 1 month. Defrost before reheating at 300° for 30 minutes.
What to serve with egg strata?
- Easy Homemade Ham with Brown Sugar Mustard Glaze
- Quick and Easy Tropical Fruit Salad
- Citrusy Hearts of Palm Salad
- Ruby Thyme Spritzers
- Sugar n’ Spice Broiled Grapefruit
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Caramelized Onion Mushroom and Bacon Strata
- 1/2 pound bacon chopped
- 16 ounces baby bella or button mushrooms sliced
- 1 cup caramelized onions recipe on this site (or see NOTE below)
- 5 cups stale Italian or Sourdough bread cut into 1" cubes
- 2 cups finely shredded mozzarella or Italian Blend cheese divided
- 1/4 cup chopped parsley
- 5 large eggs
- 1 1/4 cups milk
- 1/2 teaspoon kosher salt
- 1/4 teaspoon white pepper
- 1/8 teaspoon cayenne pepper
- 1/4 teaspoon dry mustard
- 1/2 teaspoon dried thyme
- 1/2 teaspoon onion powder
THE DAY BEFORE SERVING THE STRATA:
- Heat a large, heavy skillet over medium high heat. When the skillet is hot, add the chopped bacon and cook until crispy. Transfer the bacon to a dish lined with paper towels to soak up excess grease. Discard all but one tablespoon of the bacon grease.
- Add the mushrooms to the skillet and a pinch of salt. Cook, stirring occasionally until the mushrooms give up their liquid and begin to brown.
- In a large bowl, combine the cubed bread, bacon, mushrooms and caramelized onions. The caramelized onions may stick together, so with your fingers spread them apart and toss the mixture so that everything is evenly combined.
- Add the parsley and 1 1/2 cups of the cheese and toss again to distribute the ingredients evenly.
- Spray a 2 quart casserole with vegetable spray. Transfer the bread mixture to the casserole and spread evenly.
- In a small bowl, whisk together the eggs, milk, kosher salt, white pepepr, cayenne pepper, dry mustard, dried thyme and onion powder. Pour the egg mixure evenly over the strata. Cover with plastic wrap and refrigerate several hours or overnight.
- Remove the casserole from the refrigerator about half an hour before you bake it to take the chill away. Sprinkle with the remaining cheese.
- Preheat the oven to 350°. When the oven has heated, place the casserole in the center of the oven and bake for 45 minutes to an hour, or until the center has cooked through and the top of the casserole is golden and puffed.
- Remove from the oven and let rest for 10 minutes before serving.