The first thing you have to do is clean the mussels. Put them in a colander and rinse them under cold running water to remove any sand and grit. Mussels often have little threads that look like seaweed hanging off them called beards. Rip them off. The mussels should be closed; discard any that are open.
Heat 1/4 cup olive oil in a large saucepan over medium-high heat. Add the garlic and chile pepper and cook for a minute. Add the mussels, wine, and salt and pepper to taste and stir together. Bring to a simmer and cover with a lid, allowing the mussels to steam open, which should take about 5 minutes. Cook until all of the mussels are fully opened. Discard any unopened mussels. Let this cool down a bit. Remove and discard the garlic. When the mussels are cool enough to handle, shell them and discard the shells. Put the mussels in their broth and set aside.
In another large saucepan, heat the remaining 1/4 cup olive oil over medium-high heat. Add the onion, butternut squash, and salt and pepper to taste. Cook until the onion gets slightly golden, about 8 minutes. Add the pasta and mix together. Add 3 cups water, bring to a simmer and cook, stirring, until the pasta is done and the squash is fork-tender, about 12 minutes. Eyeball it here: If your ingredients need to cook longer and you need more liquid, add more water. If you want to give the soup a creamier consistency, mash half of the squash with the back of a fork.
Add the mussels and broth to the squash and pasta mixture; let it simmer for about 5 minutes to combine the flavors. Remove from the heat and add the Parmigiano before serving. Top with the parsley.
Photograph by David Malosh
Recipe courtesy David Rocco for Food Network Magazine