Spicy Linguine with Clams and Mussels

Name: Spicy Linguine with Clams and Mussels
Ingredients: 1 pound linguine pasta; 2 tablespoons unsalted butter, at room temperature; 1/4 cup chopped fresh flat-leaf parsley; Kosher salt and freshly ground black pepper; 3 tablespoons olive oil; 2 large or 4 small shallots, sliced; Kosher salt, for seasoning, plus 2 teaspoons; Freshly ground black pepper, for seasoning, plus 1 teaspoon; 3 cloves garlic, minced; 1 cup white wine (recommended: Pinot Grigio); 1 cup vegetable broth; 1/2 teaspoon crushed red pepper flakes; 12 littleneck clams, cleaned; 12 mussels, cleaned