Cook pasta shells according to package directions. Drain and cool.
Heat oil in 12-inch saucepan over medium heat. Add onions, zucchini, yellow squash, and butternut squash and cook 10 minutes or until vegetables are fork tender.
Add garlic and red pepper flakes and cook 2 to 3 minutes.
Move vegetables from pan to a platter. Carefully stir ricotta into warm vegetables being careful not to break the vegetables.
Add butter to pan and melt.
Whisk in flour, salt, pepper, and nutmeg. Cook 1 minute.
Whisk in milk and cook 2 to 3 minutes until sauce begins to thicken.
Heat oven to 375 degrees F.
Spray an 11.5x8 inch casserole dish with non-stick spray.
Pour 1 cup sauce in bottom of casserole dish.
Fill shells with squash and ricotta mixture placing each filled shell into the prepared casserole dish.
When all shells are filled, pour cream sauce over shells.
Top with mozzarella cheese.
Bake until heated through and cheese is melted.
Serve hot.
Notes
Recipe from Paula @CallMePMc.com All images and content are copyright protected. Please do not use my images without prior permission that includes copying the ingredient list or entire recipe and posting in the comments on Pinterest for Facebook. If you want to share this recipe, please simply link back to this post for the recipe.