Use this jam to fill our beautiful Gingerbread Linzertorte.
Stir together 3 cups raspberries and the sugar in a medium saucepan. Let stand 15 minutes, stirring occasionally, until berries begin to give off their juices.
Bring mixture to a boil over medium high heat, stirring occasionally. Skim off foam. Reduce heat; simmer, skimming foam occasionally, until slightly thickened, about 5 minutes.
Stir in remaining raspberries; simmer just until berries break up, about 1 1/2 minutes. Let cool completely. Refrigerate until cold, at least 4 hours or overnight.