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

Cook the sausage in a skillet over medium heat until browned. Add the mushrooms next and sauté until they're soft. Finally, stir in the spinach until it wilts down.

Whisk together the eggs and milk in a large bowl, seasoning with salt and pepper.

Spread the cooked sausage mixture evenly in your prepared baking dish. Pour the egg mixture over the sausage.

Sprinkle your shredded cheddar cheese generously over the top.

Bake for 30-35 minutes until the top is puffed and golden brown.

Cool for about 5 minutes before slicing and serving.