- Whisk cake flour, cocoa powder, baking soda and salt together.
- In another bowl whisk the buttermilk, SoCo, vanilla, vinegar, and food coloring together.
- In another (large) bowl beat the butter, gradually add sugar, beat for 3 min.
- Add eggs, one at a time. beat well.
- Alternate adding the flour mixture and SoCo mixture, starting and ending with the flour mixture. (flour, SoCo, flour, SoCo, flour).
- Fill cupcake tins 3/4 full and bake at 350 degrees for approx 20 minutes.
- Beat butter for about 2 minutes.
- Mix SoCo & milk together.
- Slowly add powdered sugar, alternating with milk/SoCo mixture, starting and ending with the powdered sugar.