This overnight sourdough breakfast casserole recipe is an ideal recipe to prep in advance for Christmas morning breakfast, weekend brunch, Mother’s Day, or another special occasion. With kale, shallots, and a mix of gruyere and cheddar cheeses, you’ll love every bite of this easy vegetarian strata!
Growing up, my mom used to make this AMAZING ham, bread, and egg casserole on Christmas morning every year. So, this sourdough breakfast casserole is sort of like my adult, fancy pants version of the Christmas morning breakfast strata I had as as kid.
I mean, it has sourdough bread AND kale. I’m pretty sure those both fall under the top 10 things millennials love to talk about and/or eat. But don’t be fooled by the ingredients, it’s incredibly easy to make! You can also prepare this strata the night before you want to eat it and let it sit in the fridge overnight. Game. Changer.
The mix of cheeses and touch of mustard add great flavor, while the bread gets fluffy and delicious from soaking up the milk and eggs. Even my toddler daughter loves this one, so you know it’s a hit! I hope you and your whole family enjoy this beautiful breakfast for a special occasion or during the holiday season. If you’re looking for another eggs + greens recipe while you’re here, check out the Baked Eggs with Swiss Chard.
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Ingredients and Substitutions
- Sourdough bread: This is the main ingredient, so try to get a good loaf from a bakery if you can. You can also use white bread or another kind of bread that you like, but it tastes best with sourdough in my opinion.
- Kale: You can use any kind of kale, curly or lacinato (dinosaur). I’ve used both kinds and like it any way it’s made! Sub spinach if you don’t want kale.
- Shallots: Sub red or yellow onion if that’s what you have.
- Gruyere and sharp cheddar cheese: If you can’t find gruyere, substitute a Swiss cheese (like baby Swiss). You can also mix up the cheeses and try gouda, parmesan, or other favorites.
- Whole grain Dijon mustard: Any kind of whole grain or stone ground mustard would probably work really well in sourdough breakfast casserole. I use the whole grain Dijon mustard from Trader Joe’s, but you can substitute regular Dijon if you want.
- Milk: I have made it with skim and whole milk. Both work well. Even non-dairy milk would work.
- Salt and pepper
Variations
If you want to add a little something extra to this strata, consider these additions:
- Cooked breakfast sausage crumbles
- Sautéed chopped mushrooms
- Chopped bacon or ham
- A pinch of cayenne pepper
- Fresh herbs
Instructions
The full recipe for sourdough breakfast casserole, including ingredient quantities, is at the bottom of the post. Here’s a preview of the steps with photos to guide you in the kitchen.
Prep the veggies. Dice the shallot and chop the kale.
Cook the kale and shallots in a skillet with some olive oil.
Transfer the cooked kale and shallots to a greased baking dish.
Add sourdough bread pieces on top of the kale.
Sprinkle with the shredded cheeses.
In a large mixing bowl, whisk together the eggs, milk, salt and pepper, and mustard.
Pour the egg mixture over the other casserole ingredients. Use a large spoon or fork to gently mix the ingredients to spread out the kale a little. Cover with foil and put in the fridge for at least 20 minutes.
Bake covered with foil for about 30 minutes. Uncover and bake for another 15 minutes until the bread is slightly browned.
Make Ahead Instructions
Sourdough breakfast casserole can easily be made in advance and stored in the refrigerator for up to 12 hours before baking. Prep it the night before, cover with foil, put it in the fridge, and simply transfer it to the oven when you wake up the next morning. However, you don’t need to let it sit overnight (20 minutes will do) if you would rather make the recipe all in one morning!
Storage and Reheating
Keep leftover pieces in an airtight container in the refrigerator for up to 3 days. Reheat in the microwave for 1-minute intervals until warmed through.
Serving
I love serving this easy sourdough breakfast casserole as part of a brunch spread with fresh fruit or juice, muffins, and other favorites. It would taste great with my Prosecco and Carrot Juice Cocktails and Oatmeal Orange Carrot Muffins with Cranberries. Explore my full breakfast category for more ideas.
More Healthy Breakfast Recipes
- Veggie Quiche
- Oatmeal Sweet Potato Muffins with Blueberries
- Baked Banana Pancakes with Lentils
- Avocado Pancakes with Cornmeal and Lime
I’d love to hear how you like this recipe! Rate/review using the stars on the recipe card or in the comments, and follow the Veg World on YouTube, Instagram, Facebook, and Pinterest. Looking for something totally different? Browse the recipe library.
📖 Recipe
Sourdough Breakfast Casserole with Kale
Ingredients
- 1 tablespoon extra virgin olive oil
- 1 medium shallot - diced
- 6 cups kale - about 1 bunch, stems removed and chopped; can use any type of kale
- 4 cups sourdough bread - cubed or roughly torn
- ½ cup shredded gruyere cheese - plus more for topping
- 1 cup shredded sharp cheddar cheese - plus more for topping
- 10 eggs
- 2 cups milk
- 2 tablespoons whole grain Dijon mustard
- ½ teaspoon salt - more to taste
- ¼ teaspoon freshly ground black pepper - more to taste
Instructions
- If you are making the strata right away and not letting it sit overnight, preheat the oven to 400 degrees F/204 degrees C. Grease the bottom of a 9×13 baking dish with cooking spray or butter.
- Heat olive oil in a large skillet over medium heat. Add the shallot and chopped kale to the skillet and cook for 7 to 8 minutes, or until the shallots are tender and the kale leaves are wilted.
- Transfer the cooked kale and shallots to the baking dish. Add the torn or cubed sourdough bread, followed by the shredded gruyere and cheddar cheeses.
- In a large bowl, whisk together the eggs, milk, mustard, salt, and pepper. Pour this mixture over the sourdough, veggies, and cheese. Gently shake the dish with your hands to promote an even distribution of the egg mixture. Use a spoon or large fork to gently mix the ingredients and move the kale around. Sprinkle a little more cheese on top if desired. Cover with foil.
- Put the covered casserole in the fridge for at least 20 minutes so the bread can soak up everything. You can keep it in the fridge overnight (up to 12 hours) if you plan to bake the strata the following morning.
- Bake the strata for 30 to 35 minutes covered in foil. Remove the foil and bake it for another 10 to 15 minutes until you see the eggs set in the middle and bubbling on the edges. Enjoy warm!
- Leave a rating or review by tapping the stars on this recipe card (above) or in the comments section (at the end of the post)!
Notes
- Store leftover slices of the strata in an airtight container in the fridge for up to 3 days. Reheat for 1-minute intervals on high in the microwave until warmed through.
- Possible additions included cooked sausage crumbles or sliced bacon or ham, a pinch of cayenne pepper (if you want some heat), and/or fresh herbs.
Nutrition
This post was originally published in December 2018. It was updated with process photos and tips in December 2023.
Wendi
This was really tasty!
Lizzie Streit, MS, RDN
Yay, so glad to hear it!
Emily
Thanks for an amazing recipe! I make this for Christmas morning every year – my entire family requests it, it’s such a hit! The only change I made to make it more “Christmas-y” was add diced red bell pepper so it comes out red and green.
Lizzie Streit, MS, RDN
Hi Emily, I’m so glad you enjoy this recipe every year! What a great idea to add red bell pepper. Thanks so much for leaving a review!
Kelley
This is the perfect brunch idea!
Lizzie Streit, MS, RDN
Thank you, Kelley! It’s one of my favorite brunch recipes.
Debbie
Have you made this with spinach or broccoli and some other vegetables? Thinking any variety would be good with the base ingredients!
Lizzie Streit, MS, RDN
Hi Debbie, I have not tried it with spinach or broccoli, but I think it would taste great! Let me know if you try it with another veggie. If you are interested, I also have a recipe for a broccoli egg bake: Easy Broccoli and Cheese Egg Bake
Sandy
Very tasty and a crowd pleaser. I will be keeping this recipe.
Lizzie Streit, MS, RDN
Hi Sandy, I’m so glad that you enjoyed it! Thanks for rating the recipe and letting me know :).