How to Make It
Heat olive oil and butter in a large Dutch oven over medium-high until butter melts and starts to foam, about 1 minute. Add shallot and prosciutto; cook, stirring occasionally, until shallot is translucent and prosciutto is crisp, about 5 minutes. Add garlic and crushed red pepper; cook, stirring often, until fragrant, about 1 minute. Add tomatoes, wine, sugar, and salt; bring to a simmer.
Add mussels to sauce. Cover and cook until mussels start to open, 4 to 5 minutes. (Discard any mussels that do not open.) Stir in 1 tablespoon parsley. Lightly toss, and spoon into 4 bowls. Top with remaining 1 tablespoon parsley and, if desired, lemon wedges. Serve with bread.