Step 1

Preheat the oven to 350°. Grease a 9-by-13-inch (or other 3-quart) baking dish with butter or nonstick spray.

Step 2

Heat a large skillet over medium-high heat. Add the sausage and break up into small pieces with a wooden spoon. Cook the meat until no pink pieces remain, 6 to 8 minutes. Add the red bell pepper and white and light green parts of the scallions and cook 3 more minutes. Transfer to a plate to let cool slightly.

Step 3

Meanwhile, whisk together the eggs, heavy cream, mustard, hot sauce, salt, black pepper, and about one-half of the remaining green parts of the scallions in a large bowl (save the rest to sprinkle on top of the casserole once baked). Gently fold 1 1/2 cups of cheese, the hash browns and the sausage mixture into the egg mixture. Transfer all to the baking dish and smooth into an even layer.

Step 4

Cover with aluminum foil and bake for 50 min. Remove the foil and top with the remaining 1/2 cup of cheese. Increase the oven temperature to 400 degrees and finish baking until the center of the casserole is set (not jiggly) and the top is slightly golden, 10 to 15 more minutes. Let rest 10 minutes, top with the remaining green parts of the scallions, then serve.