You can find balsamic glaze in the grocery store. If you want to make your own: combine ½ cup good quality balsamic vinegar with 2 tablespoons brown sugar in a small saucepan over medium heat. Stir until the sugar has dissolved. Bring to a boil then reduce heat to low and simmer until the mixture is reduced by half, about 10 minutes. The glaze should be thick and syrupy. Let cool before serving. Store in the fridge in an airtight container for up to 2 weeks.