Add the butternut squash and salt, and sauté for a few minutes. Then add garlic, turkey, Italian seasoning, pepper flakes, and black pepper, and stir until meat is fully cooked.
Add in spinach and salt until the spinach is wilted.
In a large bowl, add ricotta, egg, cheese, and a pinch of salt and pepper. Mix well.
Add the cooked squash mixture into the bowl. Mix until evenly blended.
Cook a box of jumbo shell pasta al dente. Set aside in a bowl covered in olive oil to prevent sticking.
Heat butter in a medium pan. Once melted, add in flour.
Cook the flour until it turns light brown.
Add milk to the pan and stir continuously until the sauce thickens.
Add a pinch of salt and pepper.
In a casserole dish, sheet the sauce on the bottom.
Stuff each jumbo shell pasta with the stuffing and place on top of the sauce.
Bake at 400°F/ 200°C covered for 30 minutes.
Sprinkle parmesan cheese and bake again for 5 minutes until the cheese melts.