Preheat the oven to 350F degrees. Line 14 to 15 muffin cups with paper liners and set pans aside.
Stir together the flour, baking powder, and salt in a medium bowl and set aside.
Use an electric mixer to beat the butter and sugar together in a large mixing bowl until light and creamy.
Add the egg whites, vanilla, and peppermint, and beat until well combined.
With mixer on low, beat in half of the dry ingredients followed by half of the milk and beat to combine. Add the remaining flour mixture, then the remaining milk and beat until just incorporated.
Pour half of the batter into a second bowl and beat in the cocoa powder and enough food coloring to achieve the shade of red you want.
Use four tablespoons of batter in each prepared muffin cup, alternating colors. It should go like this: 1 (scant) tablespoon of white batter, 1 (scant) tablespoon of red, 1 tablespoon white, 1 tablespoon red.
Bake 16 to 22 minutes, until a cake tester inserted into the center of the cupcakes comes out clean.
Remove cupcakes from the oven and cool completely on a wire rack before frosting them.
Peppermint Buttercream Frosting
Place the shortening in a medium mixing bowl and beat with an electric mixer until very smooth. Add 5 tablespoons of milk, the vanilla, peppermint, and salt and beat to combine.
With mixer on low, gradually beat in 4 1/2 cups of Powdered sugar. Turn mixer to medium and beat until frosting is smooth.
Add additional Powdered sugar if frosting is too thin; if it’s too thick add additional milk.
Place half of the frosting in a second bowl and beat in the cocoa powder and red food coloring. (If you don’t want to pipe the frosting you can either leave it all white or tint it all red, then just spread on top of the cooled cupcakes.)
To pipe colored swirls of frosting, transfer some of the white frosting to a 16-inch disposable piping bag and some the red frosting to a second (also 16-inch) piping bag. Don’t fill either bag more than half full.
Snip off the bottom tip of each bag and carefully place in a third disposable bag that you’ve fitted with a large open star tip.
Pipe swirls of frosting on top of your cooled cupcakes, refilling the bags with frosting as necessary. Decorate each cupcake with a mini candy cane, if desired.
Uneaten cupcakes can be stored, covered, at room temperature for up to 2 days, in the fridge, covered, for up to 3 days, or in the freezer, tightly wrapped, for up the 2 months.