Autumn Squash Lasagna

Name: Autumn Squash Lasagna
Ingredients: 1 20-ounce package turkey sausage; 1 1/2 cups onion chopped; 1 lb. mushrooms sliced; 3 cloves garlic minced; 2 1/2 tablespoons rubbed sage; 3 cups squash cooked and mashed (butternut, Hubbard, acorn, pumpkin, or kabocha); 1/2 cup ricotta cheese; 1/2 cup Parmesan cheese grated; 2 large eggs; 1/2 teaspoon salt; 1/2 teaspoon pepper; 1/2 to 1 cups vegetable or chicken broth; 1 lb. Fontina cheese shredded; 2 cups mozzarella or pizza blend cheese shredded; 1 8-ounce package oven-ready lasagna noodles; 1 pinch red pepper flakes (optional)