Step 1

Heat the oven to 375°F. Lightly coat a 9x13-inch baking dish with cooking spray or oil.

Step 2

Heat 1 tablespoon olive oil in a large skillet over medium heat until shimmering. Add 1 pound uncooked pork breakfast sausage and cook, breaking it up into small pieces with a wooden spoon, until no longer pink, 6 to 8 minutes.

Step 3

Stir in 1 diced medium yellow onion, 1 diced medium red bell pepper, and 1/2 teaspoon of the kosher salt. Cook, stirring occasionally, until the onion is softened, 3 to 5 minutes. Stir in 3 ounces baby spinach. Cook until wilted, about 1 minute. Transfer to the baking dish.

Step 4

Whisk 12 large eggs, 2 cups half-and-half, 1 tablespoon Dijon mustard, the remaining 1 teaspoon kosher salt, and 1/2 teaspoon black pepper in a large bowl until combined.

Step 5

Add 20 ounces frozen shredded potatoes (if it’s frozen into big clumps, smash the unopened bag against a hard surface to break them up first) and half of the shredded sharp cheddar cheese (about 3/4 cup) to the baking dish. Stir until combined and spread into an even layer.

Step 6

Pour the egg mixture over the potato mixture. Tilt the baking dish so the egg mixture is in an even layer if needed. Sprinkle with the remaining 3/4 cup cheddar.

Step 7

Bake until a knife inserted in the middle comes out clean and the top is light golden-brown, 55 to 60 minutes. Let cool for 5 minutes before serving.