Heat oil in Dutch oven over medium-high heat until shimmering; add lamb and onion and cook, stirring occasionally, until lamb is well browned and onion is soft and golden, about 8 minutes (reduce heat to medium if pan becomes very dark). Add wine and simmer until reduced by half, about 1 minute, scraping pan bottom with wooden spoon to loosen browned bits. Add broth and garlic paste; simmer until reduced by half, 15 to 20 minutes. Add any accumulated juices from platter with resting lamb. Strain jus through fine-mesh strainer into small saucepan; add vinegar and serve with sliced lamb, or keep warm until needed.

Makes about 2 cups