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Slow Cooker Mother’s Day Brunch Casserole

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A warm, golden, deeply satisfying slow cooker brunch casserole layered with crispy hash browns, savory breakfast sausage, sweet bell peppers, onion, and generous amounts of sharp cheddar — all baked in a rich egg custard and finished with a bubbling cheese topping. Assembled the night before in twenty minutes, cooked hands-off while the household prepares everything else, and ready to hold on WARM until every last person is at the table. The perfect Mother’s Day brunch — effortless for the cook, special for the one being celebrated.

  • Total Time: 12 hours (including overnight rest)
  • Yield: 8 – 10 servings 1x

Ingredients

Scale

The Casserole Base

  • 1 lb (450g) bulk breakfast sausage
  • 1 package (20–24 oz) frozen shredded hash browns, do not thaw
  • 1 red bell pepper, diced
  • 1 yellow bell pepper, diced
  • 1 medium onion, diced
  • 3 cloves garlic, minced
  • 1½ cups (170g) shredded sharp cheddar cheese (stirred in)
  • 2 tbsp unsalted butter

The Egg Custard

  • 8 large eggs
  • 1 cup (240ml) whole milk
  • ½ cup (120ml) heavy cream
  • 1 tsp garlic powder
  • ½ tsp onion powder
  • ½ tsp smoked paprika
  • ½ tsp dried mustard
  • ½ tsp salt
  • ¼ tsp black pepper
  • Pinch of red pepper flakes (optional)

The Cheese Topping (Added Last 30 Minutes)

  • ½ cup (55g) shredded Gruyère — OR — ½ cup additional sharp cheddar

To Finish

  • Fresh chives, snipped
  • Fresh flat-leaf parsley, roughly chopped
  • Hot sauce, for the table

Instructions

The night before:

  1. Brown the sausage. In a large skillet over medium-high heat, cook the breakfast sausage, breaking it into small crumbles, until fully browned. Drain off excess fat. Set aside to cool.
  2. Sauté the vegetables. In the same skillet over medium heat, melt 1 tablespoon of butter. Add the diced onion, red and yellow bell peppers, and garlic. Cook for 3 to 4 minutes until slightly softened and fragrant. Season lightly with salt and pepper. Set aside to cool.
  3. Make the custard. In a large bowl, whisk together the eggs, whole milk, heavy cream, garlic powder, onion powder, smoked paprika, dried mustard, salt, pepper, and red pepper flakes (if using) until smooth and well combined.
  4. Grease the slow cooker. Generously butter the bottom and sides of the slow cooker insert — more than seems necessary.
  5. Layer the casserole. Spread the frozen hash browns in an even layer on the bottom of the insert. Scatter the browned sausage evenly over the hash browns. Distribute the sautéed vegetables over the sausage. Sprinkle 1½ cups of the shredded cheddar over the vegetables.
  6. Pour the custard. Pour the egg custard mixture evenly over all the layers. Press down gently with a spatula to ensure the custard reaches all areas. Cover the insert and refrigerate overnight.

In the morning:

 

  1. Start the slow cooker. Remove the insert from the fridge and let it sit at room temperature for 20 minutes. Place in the slow cooker base. Lay 2 full sheets of paper towels across the opening. Place the lid on top, securing the paper towels between the lid and rim.
  2. Cook. Set the slow cooker to LOW and cook for 3 to 4 hours without lifting the lid. The casserole is done when the egg custard is fully set — a knife inserted in the center comes out clean — and the edges are golden and slightly pulling from the sides.
  3. Add the cheese topping. Remove the lid and paper towels. Scatter the Gruyère or remaining cheddar evenly over the surface. Replace the lid (without paper towels this time) and cook on HIGH for 20 to 30 minutes until the cheese is fully melted and beginning to bubble.
  4. Rest and finish. Turn off the slow cooker. Rest for 10 minutes with the lid slightly ajar. Scatter fresh snipped chives and chopped parsley generously over the top.
  5. Serve. Scoop generous portions into warm bowls or onto plates. Serve with hot sauce on the side and the rest of the brunch spread alongside. Sit down. Enjoy the morning.

Notes

  • Assemble the night before — it is the whole point. The overnight assembly is what makes this dish the right one for Mother’s Day. Twenty minutes the night before means a completely relaxed morning. Do not skip this step or try to make it same-morning — the overnight rest also allows the custard to soak into the hash browns more thoroughly, producing a better-textured casserole.
  • Grease generously. Egg casseroles are aggressive stickers. Use more butter on the insert walls than feels necessary. Every surface — bottom and up the sides — needs to be covered.
  • Frozen hash browns, not thawed. Thawed hash browns release moisture and produce a soggy casserole. Straight from frozen, they absorb the egg custard during cooking and become tender and creamy.
  • Paper towels under the lid. Condensation from the lid dripping onto the surface of the custard prevents it from setting properly and creates wet, unappealing patches. Two sheets of paper towels between the lid and the rim solve this completely.
  • Check doneness with a knife. The custard should be fully set — a clean knife test in the center confirms this. Slightly underdone egg custard is soft and wet; properly cooked custard is firm, puffed at the edges, and holds together when scooped.
  • The WARM setting is the brunch host’s greatest asset. Once done, the casserole holds on WARM for up to 2 hours without any quality loss. This is the feature that makes a slow cooker brunch casserole so ideal for a relaxed occasion — there is no pressure to serve immediately.
  • Let her sit. The whole point of this recipe, on this particular morning, is that someone else did the work. Make it beautiful. Set the table. Pour the coffee. And let the person being celebrated simply enjoy.
  • Author: Elle
  • Prep Time: 25 minutes (night before)
  • Cook Time: Overnight Rest 8 hours - Cook Time- 3 hours 30 minutes (on LOW + cheese melt)
  • Category: Breakfast, Brunch, Holiday
  • Method: Slow Cooking
  • Cuisine: American
  • Diet: Gluten-Free

Find it online: https://slowcookerrecipes.us/slow-cooker-mothers-day-brunch-casserole/