In a small saucepan, over medium heat, simmer the vinegar and the garlic. Simmer until reduced to a thick syrup, about 5 minutes. Set aside while the rest of the meal is being finished.

When ready to serve the sauce, rewarm over  medium-low heat. Cut a stick of butter into 6-8 pieces and add to the balsamic reduction one piece at a time. Whisk until all butter is incorporated and sauce is smooth again. Season with salt and pepper if needed.

Drizzle over plate right before serving.