In a large bowl, use an electric mixer to beat the butter until smooth and fluffy. Gradually mix in confectioners sugar and cocoa powder. Add 2 Tablespoons of heavy whipping cream; beat for an additional 3-4 minutes until stiff peaks form.
Add up to another tablespoon of heavy whipping cream if needed to thin out the buttercream.
Spoon buttercream into a piping bag fitted with a round tip. Pipe the frosting onto the cupcakes.
To decorate:
Using white decorating gel, draw a dot for the base of each eye on the peanut butter cups. Then, add a small black dot for the pupal using black decorating gel. Using the white decorating gel again, pipe on a tiny white dot in the center of the pupil.
Use black decorating gel to attach a Sweet Tart in the center of each peanut butter cup as the nose.
Continue with black decorating gel, drawing on whiskers and a smile (eyebrows are optional).
Set bunny faces aside to allow decorating gel to dry.
Press Whoppers into the frosting on either side to form the bunny’s hands.
Place peanut butter cups on cupcakes.
Use a rolling pin to flatten Tootsie Rolls. Use a knife to cut into ear shape. Place ears into the freezer for 5 minutes to harden.
Melt chocolate in the microwave by heating in 30-second incriments, stirring after each, until completely melted.
Remove ears from freezer, bend into desired shape, dip bottom into melted chocolate, and place on the top of the peanut butter cup.
Notes
Use a boxed chocolate cake mix and premade chocolate frosting to save time.
You can use candy eyes instead of making the eyes with the decorating gel.