Heat grill to high. Heat the oil in a heavy Dutch oven on the grates of the grill until shimmering. Add the lemongrass, curry paste, wine, coconut milk, fish sauce, and lime juice and bring to a simmer, whisking. Add the mussels, cover the pot, and let steam until opened. During the last minute of cooking, add the cilantro and basil. Serve from Dutch oven into individual bowls, discarding the lemongrass.