Heat the oil in a large high-sided Dutch oven over medium heat until it begins to shimmer. Sweat the shallots and garlic by cooking for about 30 seconds. Add the mussels and wine; stir to combine.
Cover and cook, shaking the pot occasionally, until some of the mussels start to open, about 2 minutes. Sprinkle with the parsley and red chile flakes. Add the butter, cover and cook until all the mussels have opened and the flavors have infused, 1 to 2 more minutes.
Transfer the mussels to a large serving dish, discarding any that didn't open. Ladle the broth over the mussels and serve with chunks of the torn baguette.