Preheat oven to 350 degrees F and brush a 9 by 13" baking dish with olive oil. Bring a large pot of salted water to a boil. Cook the shells according to package directions and rinse under cold water when finished.

To make the filling: Bring olive oil to medium heat in a large pan and sautee spinach until cooked about 1-2 minutes. Set aside.

To make the butternut squash sauce: heat olive oil over medium heat in a large pan (same pan) and add the onions, cook until soft and translucent about 5-7 minutes. Add the garlic and cook for another minute. Add the cubed squash season with salt, pepper, cinnamon, and nutmeg tossing to coat, add the stock and bring to a simmer, cover and cook 15-20 minutes until soft. Let slightly cool and transfer to a blender, blend until smooth and adjust seasoning to taste if needed. pour into baking dish about half way up the edges.

To make the stuffed shells: Combined cooked spinach, ricotta, walnuts and sage into a bowl and whip until fluffy and combined. Add a generous tablespoon of the mixture into each shell and place into the sauce. Bake for 20 minutes until the sauce bubbles and shells start to get golden.

Serve with fresh parmesan and lay a fresh leave of sage over each shell.