Pasta with Clams and Mussels Mariniere

Name: Pasta with Clams and Mussels Mariniere
Ingredients: 1/2 pound mussels; 4 tablespoons unsalted butter; 2 tablespoons extra-virgin olive oil, plus more for pasta water; 2 shallots, minced; 4 cloves garlic, minced; Pinch dry red pepper flakes; 1/2 pound clams; 2 sprigs tarragon, leaves stripped; 1 sprig thyme, leaves stripped; 1 sprig fresh rosemary; 1/2 cup dry white wine; 12 ounces fresh fettucine; Salt; Freshly ground black pepper; 1 tablespoon minced fresh parsley; 2 teaspoons minced fresh tarragon leaves; 1/4 cup grated Parmesan