In a large skillet, heat the oil over medium-high heat. Add the onions and cook, stirring, until caramelized, about 15 minutes. Add the garlic and cook, stirring, for 1 minute. Add the stock and bring to a boil. Cook, stirring, occasionally, until reduced by 1/2. Add the honey, mustard and vinegar, and reduce heat to medium-low. Simmer until thickened, about 6 minutes. Remove from the heat and cool for at least 10 minutes before serving with the sausages.
Yield: 1 cup