Cheesy Sausage and Butternut Squash Casserole | Love2Feed

Ingredients

• 3 tablespoons extra-virgin olive oil
• 1 medium red onion
• 1 pound spicy Italian sausage, casings removed
• 10 ounces frozen diced butternut squash (about 1 1/2 cups)
• One 15-ounce can crushed tomatoes
• Salt and freshly ground black pepper
• One 16-ounce tube ready-made polenta
• 1 tablespoon unsalted butter, cut into small pieces, plus more for greasing the dish
• 5 ounces fontina cheese, thinly sliced (1 1/4 cups)
• 1 ounce grated Parmesan (about 1/4 cup)
• 5 ounces baby spinach (about 6 cups)
• 2 teaspoons balsamic vinegar
• Special Equipment:
• Special eA 2-3 quart broiler-safe baking dish