PREHEAT & PREP. To start, preheat the oven temperature to 350 degrees F. lightly grease a 9x9 baking dish. I like a glass or ceramic 9x9 casserole dish for this, since it conducts heat more gently!
BROWN THE SAUSAGE. In a large skillet, brown the sausage over medium heat until it's fully cooked through and slightly crispy on the outside. Drain excess grease from the pan and add cooked sausage to the bottom of the baking dish.
WHISK EGG MIXTURE. While the sausage cooks, prep your other ingredients. In a large bowl, combine eggs, egg whites, cottage cheese, salt and pepper. Make sure the egg whites are well blended. Pour egg mixture over the sausage. (If desired, you can cover the dish with plastic wrap or aluminum foil and chill the casserole overnight at this point and finish it in the morning.)
ASSEMBLE. Right before baking, sprinkle the egg mixture with cheddar cheese and add the hash brown patties on top. You should be able to fit 6 patties in a 9x9 pan!
BAKE. Place the egg bake in the preheated oven and bake 40-45 minutes, or until the center is just set and only has a tiny wobble. (You don’t want it to slosh or look liquid.) Let the egg bake stand 5-10 minutes before cutting into slices.
SERVE & STORE. Cut into 6 slices (I just slice in between the hash brown patties!) and serve warm. Store leftovers in an airtight container in the fridge 2-3 days.