Diced breakfast potatoes with bell peppers make the bottom crust, layered with cooked breakfast sausage, a mustard/herb/egg mixture next, and finally topped with French gruyere cheese and Swiss cheese.
Beat eggs, mustard, seasonings, and cream in a large bowl.
In a 9x13 casserole baking dish layer potatoes in the bottom of the pan and then evenly spread out the cooked sausage on top.
Pour the egg mixture evenly into the dish and top with shredded cheese.
Bake in a 400-degree F oven for 30-40 minutes until bubbly and golden brown.
Notes
If you are making this the night before, cover it with aluminum foil and put it into the refrigerator. The next day bake as directed. The cook time may vary depending if you start with a room temperature or cold casserole. To cook the sausage - place the sausage in a large skillet (12" cast iron skillet) over medium-high heat. Brown sausage until cooked through. Remove the hot sausage from the grease and let cool. Add to the casserole. Make sure to whip the egg mixture until bubbles form in the mixing bowl for fluffy eggs.Use up to 1 1/2 cups of cheese if you like more cheese!Dry mustard can replace fresh.