Blue Velvet Cupcakes with Marshmallow Frosting

For the cupcakes:
Preheat oven to 350ºF. Line a standard muffin pan with paper liners.

In a medium bowl, sift together cake flour, cocoa powder and salt; set aside. In the the bowl of an electric mixer fitted with the paddle attachment, cream the butter and sugar together on medium-high for 2-3 minutes until light and fluffy.

Add egg in and mix for about another minute. Next add vanilla extract and food coloring, continue mixing until combined. At low speed, add in 1/3 of the dry ingredients, then half the buttermilk, mixing after each addition. Continue this pattern until everything is just combined (finishing with the dry).

In a small bowl, combine the vinegar and baking soda (it will foam up) and add it to the batter. Mix batter for another 10 seconds on medium.

Distribute the cupcake batter evenly among wells. Bake for about 20 minutes (or until inserted toothpick comes out clean). Allow cupcakes to cool in the pan for 5-10 minutes, then transfer to a wire rack until room temperature.

For the frosting:
In the the bowl of an electric mixer, beat butter with the paddle attachment on medium until fluffy. Reduce speed to low, add sugar slowly until sugar is moistened. Continue to mix at medium-high speed until combined. Add marshmallow fluff and vanilla. Continue to beat frosting until blended and smooth (add more powdered sugar if it’s too thin or runny). Transfer frosting to pastry bag fitted with a large decorating tip. Top each cupcake a swirl of frosting.

Notes:
Gel colors saturate much better, so you don’t have to use as much. When you add just blue, it turns a little greenish. So after you add some blue, just add a little violet to make a “royal blue” (mine ended up more a of a navy because I was a little heavy-handed). They get a bit darker when they bakes also.

If you don’t have buttermilk, you can make your own (which is what I did). Combine 1/2 scant cup milk with 1-1/2 teaspoons white vinegar. Mix to combine and let it stand for 5 minutes before using.

Store cupcakes in an airtight container for 2-3 days at room temperature (or they can be frozen up to 2 months without frosting).

Adapted from Martha Stewart.