Here's a good base recipe for using frozen berries to prepare a flavorful sauce. I find that frozen berries need to cook a little to make them less watery and to concentrate their flavor. Look for raspberries that come frozen in a bag. Feel the bag to make sure all of the individual berries are loose and not clumped together. Bags of frozen berries tend to taste better than those frozen in a block.
Variation
Substitute a 12-ounce bag of strawberries or blueberries for the raspberries. Don't use Kirsch or Framboise with blueberries, though a dash of white rum works nicely.
