Sausage Pizza Au Gratin Potato Casserole
- 1 pound ground hot Italian sausage
- 3 tablespoons olive oil, divided
- 8 ounces sliced baby Portobello mushrooms
- 5 red Idaho® potatoes, cut into ½-inch cubes (about 5 cups)
- 1 large onion, chopped
- 1 green pepper, chopped
- 2 cloves garlic, minced
- 1 teaspoon red pepper flakes
- ½ teaspoon dried Italian seasoning
- 1 (28-ounce) can pizza sauce
- ¼ cup grated Parmesan cheese
- 2 cups mozzarella cheese, divided
- ¼ cup chopped parsley for garnish
- salt and pepper
- Preheat oven to 350° F. Lightly grease a 9-inch-by-13-inch casserole dish.
- Heat a large skillet over medium-high heat. Add the sausage to the pan and cook, breaking the meat up as you go along, until brown, about 7-10 minutes. Using a slotted spoon, transfer the sausage to your prepared casserole dish.
- Add 1 tablespoon of olive oil to the pan. Stir in the mushrooms. Continue to cook, stirring occasionally, until tender and brown, about 5 minutes. Refrain from seasoning with salt until the end of the cooking process. Transfer the browned mushrooms to the casserole dish with the sausage.
- Add the remaining 2 tablespoons of olive oil to the pan. Stir in the potatoes. Season with a generous pinch of salt and pepper. Cook, stirring occasionally, for 12 minutes.
- Add the onion, green pepper, garlic, and red pepper flakes to the pan with the potatoes; stir to combine. Continue to cook, stirring often, until the potatoes are fork tender, about 10 minutes.
- Stir in Italian seasoning, pizza sauce, Parmesan cheese, and 1 cup of mozzarella. Continue to cook for 3 minutes. Season with salt and pepper to taste.
- Transfer the mixture to the prepared casserole dish with the sausage and mushrooms; stir to combine. Top with the remaining mozzarella cheese. Bake for 30 minutes uncovered. Sprinkle with fresh parsley, if desired.