HEAT oven to 350°F.
PREPARE cake batter as directed on package. Add dry pudding mix, 2/3 cup peanut butter and sour cream; mix well. Spoon into 24 paper-lined muffin cups.
BAKE 20 to 25 min. or until toothpick inserted in centers comes out clean. Cool cupcakes in pans 10 min.; remove from pans to wire racks. Cool completely.
MIX remaining peanut butter and frosting until blended; spread onto cupcakes. Top with jelly.