Preheat oven to 350 degrees and spray the mini Bundt pan with pam baking spray.
Using a medium bowl and hand mixer, beat the cake mix, eggs, milk and butter until combined and smooth.
Spoon some of the batter into the piping bag and cut the tip off.
Fill the cavities in the Bundt pan about 3⁄4 way full.
Bake in the oven for about 15-20 minutes or until a toothpick comes out clean.
Allow to cool before removing them and baking 6 more mini Bundt pans.
Once all 12 Bundt cakes have been made, place them onto a cookie sheet.
Using a standing mixer, beat the butter, powdered sugar, cocoa powder, vanilla extract, and heavy whipping cream.
Beat on medium speed until combined, smooth and holds a peak.
Scoop about 1 1⁄2 C of the chocolate frosting into the piping bag with the 1A tip and set aside.
Scoop the remaining frosting into the larger piping bag with 1M tip.