Place squash into 6 quarts of water and bring to a boil. Cook until squash is fork tender.
When squash is tender, drain and transfer to bowl of blender, when it has cooled slightly add in 1 cup of the stock, garlic, parmesan, olive oil and a dash of salt. Blend until smooth and creamy, adding more stock as needed if sauce is too thick or if you like a thinner sauce. Taste and add more salt as needed.
Transfer to bowl, cover and keep warm.
Pre-heat oven to 350 degrees and spread oil in a small baking dish.
While squash is cooking heat oil in a skillet over medium heat. Sauté onions until translucent, add the minced garlic to pan and sauté until fragrant, about one minute.
Add chopped kale to the pan and sauté until it starts to wilt. Season with salt and pepper to taste. Add a bit of water or vegetable stock as needed to prevent vegetables from sticking to bottom of pan.
In a large bowl toss the pasta, 3 cups of the butternut sauce and kale until well combined.
Spoon half of the mixture into the baking dish. Sprinkle on half of the cheese, top with remaining pasta and top with cheese.
Bake 15 to 20 minutes or until cheese is melted and top starts to brown.