In a saucepan over medium heat, bring the vinegar and brown sugar to a low boil. Whisk until the sugar is dissolved and reduce by half to produce a syrup.
Reduce the heat to low and stir in the pre-heated beef broth, (I do this in the microwave until it's about 110 degrees F.) Then stir in the tamarind paste, garlic, and the ginger. Allow to reduce just a little and then strain the sauce into a serving bowl.
NOTE: Tamarind sauce can be obtained at an ethnic grocer (some sell online).