1cup2 sticks of unsalted butter(2 sticks) Softened
3cupspowdered sugarsifted
1/4teaspoonsalt
1tablespoon vanilla extract
4tabelspoonmilk
Food Coloring gel in the colors that you wish - I used green and yellow
Instructions
Cupcakes
In a large bowl mix cake mix, flour, sugar, salt, water, vegetable oil, vanilla extract, sour cream, and egg whites until well blended.
Add cupcake liners to your cupcake tin.
Scoop your cupcake batter into the prepared cupcake tin. Make sure not to get them more than 3/4 full.
Bake at 325 degrees for about 18 minutes, or until a toothpick inserted into the cupcake comes out clean.
Allow to cool before adding icing.
Icing
Beat the butter for a few minutes using your mixer on medium speed.
Add 3 cups of powdered sugar and mix on low speed until blended.
Add the vanilla extract, salt, and 2 tablespoons of milk. Mix on medium speed for 3 minutes.
If you need stiffer frosting, add the remaining sugar.
If you need a thinner frosting, add the remaining milk.
Notes
If you plan on make the Multi-Colored Swirl, I suggest make 2 separate batches of icing and color each batch what you want. That way you don't have to worry about making more and making the colors match.