Preheat the oven to 350 degrees.  Cut butternut squash lengthwise and remove seeds using a spoon.  Place squash cut side down in a baking dish with 2 cups of water poured into the dish.  Bake for 30-40 minutes or until soft enough to scoop out using a spoon.

In a high-speed blender, add 2 cups cooked squash, ground mustard, coconut milk, sea salt, nutritional yeast, onion and garlic powders.  Blend on high until creamy and no chunks remain. Scrape sides during blending as needed. 

Cook pasta according to package instructions.  Drain pasta in a colander.

In a baking dish add the cooked noodles, shredded leftover turkey, cheese sauce (butternut squash mixture), sea salt and coarse ground pepper.  Using a large spoon, stir until noodles are evenly coated with sauce. Add the fresh rosemary sprigs to the top of the casserole.  Bake in the oven (350 degrees) for 10-15 minutes or until heated through. Serve.