• Preheat oven to 350 degrees. Line one standard size muffin tin with cupcake liners, set aside.
• In the bowl of a stand mixer, cream butter and sugar until light and fluffy, about 2 minutes. Add vanilla, then eggs one at a time until incorporated.
• In a small mixing bowl whisk together flours, baking powder and salt. With mixing speed on low alternate adding dry ingredients and wet ingredients (milk and sour cream). Mix until no flour pockets remain.
• Remove bowl from stand and evenly divide the batter between six bowls. Color each bowl as desired (I used six colors: red, orange, yellow, green, blue, purple) and then place a layer of each into every cupcake liner. The batter should fill each about 2/3 of the way full.
• Place in oven and bake for 18-22 minutes or until the edges become lightly golden in color and the tops spring back. Be careful not to over bake! They will look slightly moist in the center. Remove from oven and allow to cool in pan for 3 minutes before transferring to a wire rack to cool completely.

For Vanilla Buttercream

• In the bowl of a stand mixer fitted with the whisk attachment, beat butter until smooth, about 1 minute. With mixing speed on low, add vanilla, salt and powdered sugar. The mixture will look clumpy, that's ok. Add the heavy cream and gradually increase mixing speed to high. Beat for 2-3 minutes or until the frosting is light and fluffy. Remove and pipe (or spread) onto cooled cupcakes. Top with desired sprinkles.