Polenta Pizza

Ingredients (8)

• + 1 tablespoon olive oil add to pantry
• + 1 Spanish onion, thinly sliced add to pantry
• + 1 green bell pepper, thinly sliced add to pantry
• + 1 (3.5 ounce) link hot Italian sausage, sliced add to pantry
• + ¼ cup sliced fresh mushrooms, or more to taste add to pantry
• ✓ 1 slice prepared polenta, cut into 4x4-inch piece
• + ¼ cup spaghetti sauce, or as needed add to pantry
• + 1 ounce shredded mozzarella cheese add to pantry