Sausage and Chard Stuffed Shells in Butternut Squash Sauce

0 Preheat oven to 400° F. Spread butternut squash sauce on the bottom of a large oven-safe skillet or 9 x 13 inch baking dish.
2 Cook pasta according to package directions.
4 While pasta boils, heat a large saute pan over medium heat. Add sausage, breaking it apart with a spatula while it cooks. Cook until golden brown and crumbled, about 5 minutes. Transfer sausage to a large mixing bowl and return pan to heat. Add butter and, when it melts, add onions and cook until onions are tender, about 5 minutes more. Add chard and cook until chard wilts, about 2 minutes (add the lid to help it cook faster). Add chard mixture to the sausage. Top with mozzarella and ricotta and stir to combine.
6 Spoon filling into a large plastic bag and seal the bag. Cut a triangle out of one of the bottom corners of the bag. Hold one pasta shell at a time in your hand and use the other hand to squeeze filling from the plastic bag into the shell. (You can also just spoon the filling into the shells if you prefer.)
8 Arrange the filled shells on top of the butternut squash sauce. Bake until the dish is warmed through and the shells are just beginning to turn golden brown on the tops, 12 to 15 minutes.
10 Serve immediately, with parmesan cheese on top.