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Over the years it’s become our tradition: the scent of sage sausage and sharp cheddar wafting through the house while we lounge in pajamas, trading stories about the night before. Friends have started requesting it by name; my neighbor once joked she’d trade babysitting hours for a corner piece with the crispy edges. Whether you’re feeding a crowd of overnight guests or simply want a stress-free way to celebrate the first morning of the year, this casserole delivers big, cozy flavor with almost zero morning-of effort.
Why This Recipe Works
- Make-ahead magic: assemble up to 24 hours in advance and simply bake in the morning.
- Feeds a crowd: one 9×13 pan yields 12 generous slices—perfect for buffet-style serving.
- Balanced flavors: savory sausage, sweet peppers, earthy mushrooms, and a hint of mustard heat.
- Texture contrast: custardy interior crowned with a golden, cheesy top layer.
- Customizable: swap in your favorite veggies, cheeses, or meats without fuss.
- Freezer-friendly: bake, cool, and freeze portions for up to two months.
- Egg ratio tested: exactly 10 eggs for a sliceable yet tender custard that never feels rubbery.
Ingredients You'll Need
Great casseroles start with great building blocks. Below, I’ve broken down each star ingredient and why it matters.
- Day-old challah or brioche (12 oz): These eggy, buttery loabs soak up the custard without falling apart. Tear into 1-inch pieces and leave uncovered on the counter overnight so they stale slightly—this prevents a soggy bake. No challah? A sturdy sourdough or even everything-bagel halves work.
- Breakfast sausage (1 lb): Look for links with sage or maple; remove casings and crumble while browning. For a lighter take, turkey sausage adds 14 g protein per link with half the saturated fat.
- Sharp cheddar (2 cups grated): Buy a block and grate yourself. Pre-shredded cellulose coatings can impede melting. Aged white cheddar gives an extra tang, but orange cheddar photographs cheerfully.
- Large eggs (10): Organic pasture-raised eggs have richer yolks that tint the custard sunset-yellow. Room-temperature eggs whisk more smoothly into dairy.
- Whole milk (2 cups): Fat equals flavor and silkiness. Swap 1 cup with half-and-half for an even more decadent version, or use 2 % plus 2 Tbsp melted butter in a pinch.
- Dijon mustard (2 tsp): A whisper of heat and acidity to balance all that dairy. Whole-grain Dijon adds pops of texture if you like.
- Bell peppers & onions (1 cup each, diced):strong> Frozen diced mirepoix works if you’re short on chopping time. Roast extra peppers on New Year’s Eve and stash in the fridge.
- Cremini mushrooms (8 oz): Their earthy depth complements sausage. Wipe clean with damp paper towels; washing makes them spongy.
- Seasonings: kosher salt, black pepper, smoked paprika, and a pinch of nutmeg. Nutmeg whispers “bakery” without screaming dessert.
How to Make Make Ahead Breakfast Casserole for New Year's Day Brunch
Prep your pan and bread
Butter a 9Ă—13-inch ceramic or metal baking dish. Arrange torn challah in an even layer; set aside so it continues to air-dry while you cook the mix-ins.
Brown the sausage
Heat a large skillet over medium. Add sausage, breaking into pea-size crumbles. Cook 6–7 min until no pink remains. Transfer with slotted spoon to a bowl, leaving drippings.
Sauté vegetables
Add onions and peppers to drippings; cook 4 min until edges brown. Stir in mushrooms, ½ tsp salt, and smoked paprika; cook 5 min until mushrooms release liquid and it evaporates. Cool 10 min.
Build layers
Scatter half the sausage over bread, followed by half the veggies and 1 cup cheese. Repeat with remaining sausage, veggies, and cheese. Press lightly so fillings nestle between cubes.
Whisk custard
In a large bowl whisk eggs until homogenous and slightly frothy. Whisk in milk, mustard, 1 tsp salt, ½ tsp pepper, and nutmeg. Pour evenly over casserole; gently press bread to absorb.
Cover & chill
Spray underside of plastic wrap with nonstick spray to prevent cheese from sticking. Wrap dish tightly and refrigerate at least 4 hours or up to 24. The longer it rests, the better the texture.
Bake from cold
Next morning, preheat oven to 350 °F. Remove plastic, cover with foil, and bake 30 min. Uncover and bake 25–30 min more until center puffs and a knife inserted comes mostly clean.
Rest & serve
Let stand 10 min to set custard. Garnish with chopped chives or parsley for color. Slice into 12 squares and serve with mimosas and a side of fresh fruit.
Expert Tips
Start cold for even baking
Placing a cold casserole into a fully preheated oven prevents the edges from over-browning before the center cooks.
Weigh your bread
A full one-pound bakery loaf minus crust equals roughly 12 oz. Too much bread drinks the custard; too little yields soupy squares.
Strain vegetables
After sautéing, tilt pan and blot excess moisture with a paper towel. Extra liquid can pool at the bottom, making custard weep.
Don’t skip the rest
Ten minutes of patience lets proteins set so squares hold their shape when cut. Serve too soon and you’ll have delicious scrambled soup.
Use a digital probe
Center should reach 185 °F for fully set custard but still creamy. If top browns too fast, tent loosely with foil.
Add color last
Reserve a handful of colorful veggies (red bell pepper confetti) to sprinkle on top before baking for Instagram-worthy contrast.
Variations to Try
- Tex-Mex: sub chorizo for sausage, pepper-jack for cheddar, add 1 cup roasted corn and 2 Tbsp chopped cilantro. Serve with salsa verde.
- Mediterranean: Swap sausage for spinach-feta chicken sausage, add sun-dried tomatoes, swap mozzarella & feta for cheddar, season with oregano.
- Winter greens: Replace mushrooms with ribbons of kale and roasted butternut squash; use Gruyère and a pinch of nutmeg.
- Bagel brunch: substitute cubed everything bagels, add lox pieces and capers, use cream cheese cubes in place of half the cheddar.
- Vegetarian: Omit meat, add 1 cup sautéed zucchini and ½ cup chopped artichoke hearts; boost flavor with 1 Tbsp soy sauce in custard.
Storage Tips
Refrigerator: Cool leftovers within 2 hours, cover tightly, and refrigerate up to 4 days. Reheat individual slices in microwave 45–60 sec or in air-fryer 3 min at 325 °F for crispy edges.
Freezer: Wrap baked & cooled squares in plastic, then foil, and freeze up to 2 months. Thaw overnight in fridge and reheat at 325 °F for 15 min or until center is hot.
Make-ahead unbaked: Assemble, wrap (plastic then foil), and freeze up to 1 month. Thaw 24 hr in fridge before baking as directed. Add 10 extra minutes if still chilly.
Frequently Asked Questions
Make Ahead Breakfast Casserole for New Year's Day Brunch
Ingredients
Instructions
- Prep: Butter a 9Ă—13-inch baking dish. Spread torn bread in an even layer.
- Cook sausage: In skillet over medium heat, crumble and brown sausage 6–7 min; transfer to plate.
- Sauté veggies: In same skillet cook onion & bell pepper 4 min; add mushrooms, salt, paprika; cook 5 min. Cool 10 min.
- Layer: Top bread with half of sausage, veggies, and 1 cup cheese. Repeat layers; press gently.
- Make custard: Whisk eggs, milk, mustard, salt, pepper, nutmeg; pour over casserole. Cover with plastic wrap (coated with spray) and refrigerate 4–24 hours.
- Bake: Preheat oven to 350 °F. Remove plastic, cover with foil, bake 30 min. Uncover and bake 25–30 min more until center is set and top is golden. Rest 10 min, garnish, and serve.
Recipe Notes
For extra crunch, toss ½ cup crushed cornflakes with 1 Tbsp melted butter and sprinkle on top before baking.
