How to Make It
Heat grapeseed oil in a large saucepan over medium-high. Add onions, and cook, stirring occasionally, until browned, 5 to 6 minutes. Add sugar and salt; stir to coat. Add chicken stock, and cook until stock has reduced by about one-fourth and onions have softened, about 6 minutes. Stir in wine, and cook until reduced by one-fourth, about 6 minutes. Stir in vinegar, and cook until sauce is slightly reduced and onions are glazed with syrup, 20 to 24 minutes.