Heat two tablespoons butter in a large pot over high heat. Add two cloves of garlic and sauté, stirring constantly, for one minute. Add the broth and water; bring to a boil. Add the pasta and boil until the pasta is cooked. Lower the heat and simmer until most of the liquid is absorbed. Do not drain – there should be some liquid left in the pan to help coat the noodles.
Rinse and scrub mussels under cold water. Using your fingers or paring knife, remove beards (strings that hang from the mussel shells), and discard.
In a large stockpot set over medium heat, combine wine, shallots, garlic, and salt. Simmer 5 minutes.
Add mussels, cover, and increase heat to high. Cook until all mussels are open, about 5 minutes.
Stir in herbs and butter. Remove from heat.
Divide pasta between four bowls and add mussels. Serve immediately.