In a large, deep skillet, heat 1 tablespoon of the olive oil until shimmering. Add the scallions and cook over moderate heat, stirring, until softened, about 3 minutes. Add the wine and vinegar and boil over high heat until reduced to 2 tablespoons, about 3 minutes. Add the cream and cook until reduced by half, about 2 minutes. Stir in the butter; season the sauce with salt and pepper.