How to Make It
In a large saucepan, combine the sake, soy sauce, sugar, ginger, chiles and garlic and bring just to a boil, whisking to dissolve the sugar. Add the clams, cover and cook over high heat, shaking the pan occasionally, until the clams open, 3 to 5 minutes. Using a slotted spoon, transfer the clams to shallow bowls; discard the chiles and any clams that do not open.
Add the butter to the saucepan and cook over moderate heat, whisking constantly, until incorporated, about 2 minutes. Season the sauce lightly with salt, then ladle over the clams and garnish with minced scallions; serve right away.