Keto Sausage Breakfast Casserole

Preheat your oven to 375F and grease a casserole dish; set aside. Brown sausage in a large skillet over medium heat until almost cooked through. Add cabbage, zucchini and onion, cooking until vegetables are tender and sausage is fully cooked. Remove from heat and spoon into prepared casserole dish, then set aside. In a mixing bowl, whisk eggs, mayonnaise, mustard, sage and pepper until smooth. Add 1 cup of the grated cheese to the egg mixture and stir. Pour this mixture over the sausage and vegetables in the casserole dish. Top casserole with the remaining ½ cup cheese. Place casserole in preheated oven and bake 30 minutes, or until bubbling around the edges and the cheese is melted and lightly browned on top. Remove from the oven and serve immediately.