1-Preheat your oven to 350°F (175°C) and grease a 13×9-inch baking dish.

2-In a large skillet, cook the bulk pork sausage over medium heat until no longer pink, about 6 8 minutes. Break it into crumbles as it cooks. Once cooked, drain the excess fat and transfer the sausage to the prepared baking dish.

3-In the same skillet, heat butter over medium-high heat. Add the chopped onion and sliced fresh mushrooms. Cook and stir until tender, approximately 3 5 minutes.

4-Add the thawed and thoroughly squeezed spinach to the skillet with the vegetables. Stir until combined and heated through.

5-Spoon the vegetable mixture over the sausage in the baking dish, spreading it evenly.

6-In a large bowl, whisk together the 12 large eggs and 2 cups of 2% milk until well blended.

7-Pour the egg mixture evenly over the vegetables and sausage in the baking dish.

8-Sprinkle the shredded Swiss cheese and shredded sharp cheddar cheese over the top of the casserole, followed by the paprika.

9-Bake uncovered for 30 35 minutes, or until the center is set and a food thermometer reads 165°F (74°C).

10-Remove the casserole from the oven and let it stand for 10 minutes before serving. This resting time helps the casserole set and makes cutting into portions easier.