HEAT oven to 350°F.
PREPARE cake batter and bake in 24 paper-lined muffin cups as directed on package. Cool just 30 min. (Cupcakes need to be warm when filled.)
BEAT pudding mix and milk with whisk 2 min. Add peanut butter; mix well. Spoon into small freezer-weight resealable plastic bag; snip off one bottom corner of bag. Insert tip of bag into centre of each cupcake, then squeeze bag to pipe about 1 Tbsp. filling into cupcake.
MICROWAVE Cool Whip and chocolate in small microwaveable bowl on MEDIUM 1-1/2 min. or until chocolate is completely melted and mixture is well blended, stirring after 1 min. Dip tops of cupcakes in glaze; sprinkle with nuts.
serving size = 1 cupcake (65 g)