In food processor or blender, process raspberries until pureed. Transfer to top of double boiler and cook, stirring occasionally, 8 minutes. Stir in maple syrup and vanilla.
In small bowl, dissolve kudzu in 1⁄4 cup cold water. Stir into raspberries. Mixture will be chalky-white at first. The color will deepen as kudzu dissolves. Reduce heat to low and cook, stirring occasionally, until thickened slightly, about 3 minutes. If sauce becomes too thick, add a teaspoon water.