Heat the olive oil in a large sauté pan over medium-high heat until hot. Add the garlic and sauté briefly until light brown. Add the mussels and white wine and season with salt and pepper. Stir, then cover and cook until the mussels begin to open, about 2 minutes. As they open, transfer them with a slotted spoon to a plate. Discard any that do not open.

Cook the juices over medium-high heat until reduced by about half. Add the tomatoes and cook quickly, just until they begin to color the juice, about 30 seconds. Do not overcook or they will melt into the sauce (which is hardly a terrible crime). Add the herbs and the butter, if using. When the butter has melted, return the mussels to the pan with any juices accumulated on the plate. Stir, and toss just to reheat. Serve immediately.