Cheesy Potato Breakfast Casserole
from https://www.thekitchn.com/

This is a hearty vegetarian breakfast casserole with all the rich, deep flavor you'd usually get from meat, but even better. The flavor boost in this easy dish comes from two things: hot mustard, and sun-dried tomatoes.

This casserole is truly hearty; it's packed with more potatoes than is usually put in a casserole of this size. But the texture is still light and even fluffy, thanks to the shredded potatoes, which don't weigh this down like cubed potatoes can.

It's a great make-ahead breakfast — make a pan of this and take a wedge with you to the office every morning for a few days.

FMM: To make this with fresh Russet potatoes, in a large saucepan, cover enough russet potatoes (to equal 6 cups shredded) with water. Bring water to a boil and cook until barely tender, about 20 minutes. Do not overcook. Let cool in refrigerator overnight. The next morning, shred the potatoes.

Variations: Add or swap out ingredients with crisp cooked bacon, green peppers, etc. Use cubed potatoes instead of shredded.

1 tablespoon unsalted butter
1 small onion, diced
2/3 cup sun-dried tomatoes, preferably oil-packed, sliced into thin strips
6 cloves garlic, minced
9 large eggs
3 tablespoons hot mustard
1 cup whole milk
1 1/2 teaspoons salt
1/4 teaspoon freshly cracked black pepper
2 cups shredded Cheddar cheese
6 cups (or 1 pound) shredded frozen potatoes

Lightly grease a 9x13-inch baking dish with nonstick spray or olive oil. In a large skillet, heat the butter over medium heat until it melts and foams up. Add the onion and garlic and cook for 5 minutes, or until the onion has softened. Add the sun-dried tomatoes and cook for about 5 minutes or they are fragrant and the onion is nearly translucent and beginning to brown around the edges. Turn off the heat.

In a separate bowl, beat the eggs thoroughly with the mustard. Whisk in the milk. Stir in the salt and black pepper. Fold in the cheddar cheese, frozen potatoes, and vegetables from the skillet. Transfer the mixture to the baking dish. (At this point the casserole can be baked immediately or covered and refrigerated for up to 24 hours.)

Bake at 350°F for 35 to 45 minutes, or until the eggs are firm and the top is slightly golden. Serve immediately with a fresh salad or fruit.

Serves 8 to 10