Sourdough Discard Breakfast Casserole Recipes

So you’ve got a jar of sourdough discard giving you side-eye every time you open the fridge? Perfect. Turn that moody blob into a golden, cheesy, savory Sourdough Discard Breakfast Casserole that’s part strata, part frittata, and 100% weekend energy.

Why This Recipe is Awesome

• It uses up a solid cup of sourdough discard, which means less waste and more bragging rights. You’re thrifty and delicious—multitasking!
• The discard adds a subtle tang and tender bite—like your favorite diner casserole but with personality.
• Make it now or make it ahead: assemble the night before, bake in the morning, and pretend you wake up like this—organized and brunch-ready.

Ingredients You’ll Need

• Sourdough discard: 1 cup (unfed)—adds tang and helps the custard set.
• Eggs: 10 large—this is the backbone; don’t skimp.
• Milk or half-and-half: 1 3/4 cups—half-and-half = richer, milk = lighter.
• Shredded cheese: 2 cups (cheddar, Gruyère, or Jack)—freshly grated melts best.
• Breakfast sausage or bacon: 1 pound—cook and crumble/chop.
• Sourdough bread cubes: 6–8 cups—day-old is best; crusts on for texture.
• Veggies: 1 small onion (diced), 1 bell pepper (diced), 2 cups baby spinach (chopped) or kale.
• Dijon or dry mustard: 2 teaspoons—quiet hero that wakes up the custard.
• Seasoning: 1 teaspoon kosher salt, 1/2 teaspoon black pepper, 1/2 teaspoon garlic powder, pinch red pepper flakes (optional).
• Butter or oil: for greasing and sautéing.
• Optional flair: chopped chives or green onions, paprika on top, a few sun-dried tomatoes, or everything bagel seasoning.

Step-by-Step Instructions

1. Prep the pan and oven
   Preheat to 350°F. Grease a 9×13-inch baking dish with butter or spray. Keep it generous—melted cheese is clingy.
2. Cook the meat
   Brown sausage in a skillet over medium heat (or cook bacon until crisp). Drain excess fat but keep a teaspoon for flavor insurance. Set aside.
3. Sauté the veg
   In the same pan, sauté onion and bell pepper with a pinch of salt until softened, 3–5 minutes. Toss in spinach to wilt for 30–60 seconds. Remove from heat.
4. Build the base
   Scatter sourdough bread cubes in the prepared dish. Top evenly with sausage/bacon and the sautéed veggies. Sprinkle on 1 1/2 cups cheese.
5. Make the custard (with discard!)
   In a large bowl, whisk eggs, milk/half-and-half, sourdough discard, Dijon, salt, pepper, garlic powder, and red pepper flakes until smooth. No streaks. Whisk well so the discard fully blends.
6. Pour and soak
   Pour custard evenly over the pan, pressing down gently with a spatula so the bread soaks it up. Let sit 10–15 minutes on the counter, or cover and chill up to 12 hours for maximum flavor.
7. Bake
   Top with remaining 1/2 cup cheese. Bake uncovered 40–55 minutes until the center is set and the top is golden. If the top browns too fast, tent loosely with foil during the last 15 minutes.
8. Rest and serve
   Let it stand 10–15 minutes for sliceable squares. Finish with chives or green onions. Serve warm with hot sauce, salsa, or a dollop of Greek yogurt if you’re in your balanced era.

Common Mistakes to Avoid

• Skipping preheat. Cold oven = overbaked edges, underbaked center. Rookie move.
• Not whisking the discard smooth. Lumps mean uneven tang and texture—give it a proper whisk.
• Drenching fresh bread. If your bread is super soft, lightly toast it first. Sturdy bread = better soak.
• Overloading watery veg. Sauté down spinach/mushrooms first or you’ll get a soggy bottom (no thanks).
• Cutting immediately. Let it rest so it sets and slices cleanly. Patience = neat squares.

Alternatives & Substitutions

• Meat swaps: Try chorizo, ham, or turkey sausage. Veg-forward? Skip meat and add roasted mushrooms or broccoli.
• Cheese choices: Cheddar for classic, Gruyère for nutty depth, pepper jack for a kick, or feta for tangy pops (add feta on top at the end).
• Dairy tweaks: Use all milk for lighter, half-and-half for luxe, or go half milk/half Greek yogurt for protein and creaminess.
• Bread options: No sourdough loaf? Use any sturdy bread (brioche, French bread). Still keep the discard for flavor.
• Flavor boosts: A teaspoon of Italian seasoning, everything bagel seasoning, or smoked paprika wakes it right up.
• Make it spicy: Add minced jalapeño, swap in spicy sausage, or finish with chili crisp. YOLO.

FAQ

• Can I use active starter instead of discard?
  Sure. Active starter works fine; the flavor is a touch milder. Keep the 1-cup measure and proceed.
• Do I have to use bread if I’m using discard?
  Nope. But the bread gives structure and that classic strata texture. Without it, you’re closer to a crustless quiche—still tasty, just different.
• Can I make it the night before?
  Yes—assemble, cover, and refrigerate up to 12 hours. Bake straight from the fridge; add 5–10 minutes if needed. Look for a fully set center.
• How do I know it’s done?
  The center should be set with no liquid jiggle, and a knife inserted in the middle should come out with moist crumbs, not wet egg. The top will be lightly golden.
• Can I freeze leftovers?
  Yes. Cool completely, wrap tightly, and freeze up to 2 months. Reheat covered at 325°F until hot, then uncover a few minutes to re-crisp the top.
• What if my discard is super sour?
  Balance it with a pinch of sugar or a splash of cream. The cheese and sausage also mellow the tang.
• Can I make it gluten-free?
  Use sturdy gluten-free bread and ensure your sausage is GF. The discard can be from a GF sourdough starter—just keep the same measurements.

Final Thoughts

This Sourdough Discard Breakfast Casserole is the kind of recipe that makes you feel smugly resourceful and wildly cozy at the same time. It’s hearty, crowd-pleasing, and flexible enough to handle whatever’s in your fridge—aka the brunch MVP. Now go impress someone—or yourself—with a pan that turns “leftovers” into legend. You’ve absolutely got this.