From the moist cake to the fluffy frosting, these scream HAPPY BIRTHDAY! The perfect birthday cake flavor - without the extra work that goes into a traditional cake!
Preheat oven to 325 and fill muffin tins with cupcake liners.
Sift cake mix into a medium bowl. In a larger bowl combine, greek yogurt (or sour cream), oil, buttermilk, vanilla, and eggs and whisk until smooth. Add cake mix and mix until smooth.
Fill cupcake liners 3/4 full and bake 13-18 minutes until an inserted toothpick comes out clean.
After cupcakes have cooled completely, cream the butter for two minutes in a large bowl. Add vanilla and heavy cream and mix until smooth. Mix in powdered sugar one cup at a time until desired consistency is reached (**if piping the frosting, double the frosting recipe and look for a slightly stiffer consistency) Spread or pipe frosting onto cupcakes. Store in airtight container at room temperature.