RASPBERRY BUTTERCREAM FROSTING 1 C. raspberries; 1/2 C. softened butter; 4 C. powdered sugar; 1.; Puree raspberries in a blender/food processor.; 2. Strain seeds through fine mesh strainer. (push juice out w/ end of wooden spoon); 3. Combine raspberry juice w/butter & powdered sugar in large bowl stir/mix to combine till light & fluffy.; 4. Frost your fav. treat.