In the bowl of a stand mixer, cream together the butter, sugar, peppermint extract, vanilla and baking powder until light and fluffy.
Mix in the egg. Add in the flour and mix until fully combined.
Divide the dough in two and transfer one half into a separate bowl. Add in a little bit of the pink food gel and mix until incorporated. Keep adding the pink food coloring until it reaches your desired color.
Shape each portion into a log and wrap in plastic wrap. Refrigerate for at least 30 minutes.
Press the two dough logs together. Wrap tightly in plastic wrap and refrigerate for at least 3 hours.
Preheat the oven to 350˚F. Line a baking sheet with parchment paper.
Cut into slices and place on the prepared baking sheet.
Bake in the preheated oven for 10 minutes, or until set. Allow to cool on wire racks.