Preparation

• Melt the butter in a 6- to 8-quart pot over medium heat. Add the scallion whites and cook, stirring frequently, until tender, about 2 minutes. Add the garlic, ginger, and chile, and cook, stirring, until fragrant, about 30 seconds. Add the miso and whisk until combined. Stir in the sake and 1/2 tsp. salt. Increase the heat to high and bring to a boil. Add the mussels, cover and cook, shaking the pot once or twice, until the mussels open, about 5 minutes.
• Divide the mussels among four bowls, discarding any that did not open. Ladle the broth over the mussels and top with the scallion greens. Serve with lemon wedges and bread.