1) Preheat oven to 350 degrees and line pans with cupcake liners.
2) Sift cake mix into a small bowl and set aside.
3) Combine next five ingredients (eggs, oil, buttermilk, sour cream, and vanilla) until smooth.
4) Stir in cake mix.
5) Fill cupcake liners 3/4 full and bake for 17-22 minutes or until an inserted knife comes out clean.
6) For filling combine the next 3 ingredients (marcarpone, powdered sugar, vanilla) until smooth.
7) For Buttercream frosting (last 5 ingredients): Beat butter and cream cheese for 2 minutes. Add cocoa powder and vanilla extract and beat again. Slowly add powdered sugar until you reach your desired consistency. If it becomes too thick, add 1 tablespoon milk