I used this recipe from "The Sweet Little Book of Cupcakes" (recipes from the delicious Sweet Cupcakes in Boston) as a filling for my 4th of July cupcakes.
Berry Bash Jam
Yield: Enough to fill a dozen cupcakes.
Blackberries, Raspberries, Strawberries (de-stemmed)- 1/3 cup of each (frozen is fine)
Sugar- 1 1/3 cups
Unsalted butter- 1/8 tsp
Liquid fruit pectin- 3 tbsp (can be found in canning aisle, near Jello. Do not use powderered pectin!)
1) Chop berries in a food processor until chopped into a chunky paste (a potato masher is a fine alternative).
2) Put berries into a saucepan and place on high heat.
3) Stir in sugar, then add the butter.
4) Bring mixture to a full rolling boil (one that keeps bubbling even when stirred) and keep on high heat, stirring constantly.
5) Stir in pectin quickly, and return mixture to full rolling boil for 1 minute, stirring constantly.
6) Remove from heat and pour into a heavy duty container (plastic or glass), cover, and refrigerate.