Bring a large pot of salted water to a boil. Meanwhile, heat the butter in a Dutch oven or deep skillet over medium-high heat. Add the bacon and shallots and cook until the bacon starts to brown, about 5 minutes. Add the wine and red pepper flakes, increase the heat to high and cook until slightly reduced, about 2 minutes. Add the tomatoes, crushing them with your hands, and cook until reduced by half, about 10 minutes.
Add the pasta to the boiling water and cook as the label directs; drain. Pile the parsley, garlic and 1 teaspoon salt on a cutting board and use a large knife to mince and mash them together.
Add the mussels to the tomato sauce and stir to coat, then cover. As the mussels open (2 to 6 minutes), use tongs to transfer them to a bowl; discard any that do not open. Add the pasta to the sauce and toss until heated through, about 1 minute. Add the parsley-garlic mixture and toss. Divide the pasta among bowls and top with the mussels.