Potato and Onion Breakfast Strata

I made this dish for Christmas breakfast a couple of years ago, and it was a big hit! My grandma still talks about it, and my mom took home all my leftovers. Some of my family members are a little picky, so I kept this pretty simple, but I think it would be great if you added some mushrooms, kale, or red pepper, too!

Potato and Onion Breakfast Strata

What You'll Need:

1 sweet onion, halved and thinly sliced
1 large Yukon gold potato, peeled and diced
About 2 tbsp olive oil
1 1/2 cups (6 oz) shredded Parmesan
1 1/2 cups (6 oz) shredded Swiss cheese
8 large eggs
3 cups milk
2 tbsp Dijon mustard
Pinch of salt
Pinch of garlic powder
Pinch of paprika
1 12 oz loaf sourdough bread, cubed

How to Make It: 

Saute the onion and the potato in the oil until the potato starts to become very slightly tender and the onion just starts to turn golden, about 15 minutes. Lightly grease a 9x13 pan, and layer half the bread cubes in the pan. Spread half the onion mixture on top, then sprinkle half of each of the cheeses over that. In a large bowl, lightly beat the eggs to break up the yolks. Add the milk, the mustard, and the spices, and whisk to combine. Pour half the egg mixture over the ingredients in the pan, then repeat all the layers. Cover the pan and refrigerate it overnight (at least 8 hours, or up to 24 hours.) Take the pan out of the fridge for about 10 minutes before placing it in the oven. Heat the oven to 350 degrees, and bake the casserole, uncovered, for 45-50 minutes until a knife inserted in the middle of the strata comes out clean (the top will be lightly browned and the casserole will be set in the middle.) This recipe makes 6-8 hefty servings.