Meanwhile, make your frosting. Beat softened butter on medium speed with an electric or stand mixer. Beat for 3 minutes until smooth and creamy. Add powdered sugar, cream, and vanilla extract with the mixer running. Increase to high speed and beat for 3 minutes. Add more powdered sugar if frosting is too thin or more cream if mixture is too thick.

Once the cakes are cooled, trim off the bottoms (see photo). Use a toothpick to create 3 little holes in the bottom of the cake (don't press down too far though, you don't want it to go all the way through the cake). Then pipe the frosting into the 3 holes using a pastry bag fitted with a #21 pastry tip.

Use a butter knife to smooth the frosting, then place the cakes in the refrigerator to chill for about an hour. They’re much easier to work with when they are firm, so don’t skip this step.

Next, take the Peeps out of the package and separate them. Cut the bottoms off of the Peeps (about ⅜"). Take the cakes out of the fridge and cut a small section out to create a seat for your bunny driver. Put a little icing in the seat before placing the Peep. Cut marshmallows in half. Use icing to glue them onto car. Break the pretzels in half and stick in cake for the steering wheel.

Place in refrigerator to set for about 30 minutes before serving. Store covered in refrigerator for up to 3 days.