Preheat the oven to 375-degrees F. Spray a 13-by-9-inch baking dish with nonstick cooking spray. Set aside.
Place a large pot over medium heat. Add the squash, coconut milk, broth, and garlic. Simmer until the butternut squash is fork tender.
Transfer the squash mixture, including the liquid, to a food processor or blender. Puree until the mixture is velvety smooth.
Meanwhile, cook the macaroni to al dente (with a bite) in boiling salted water. Drain and rinse with cool water.
Spread out the macaroni in the prepared baking dish. Pour the squash puree over the pasta.
To prepare the topping: In a large mixing bowl, combine the breadcrumbs, parsley, salt, garlic, and red pepper flakes (if using). Spread evenly over macaroni. Cover the baking dish with aluminum foil.
Bake for 35 minutes until bubbly. Remove the foil from the baking dish. Sprinkle the cheese evenly over the top and bake for an additional 5 minutes.