Finely chopped peppermint candylike Hershey's candy cane kisses - this is the one I used, candy canes, or Andes peppermint crunch baking chips
Preheat oven to 350 degrees F. Line a baking sheet with parchment paper or a Sil-Pat.
In a medium mixing bowl, combine the flour, baking powder, and salt.
In a large mixing bowl, beat together the butter and sugar. Add the egg and peppermint extract. (If you are worried about your finished cookie being too peppermint-y, you can use vanilla extract instead.) Add the food coloring ad mix until combined.
Add the flour mixture in two additions, mixing until just combined each time.
If the color of the dough is not intense enough for you, add little more food coloring and mix to combine. (I ended up taking after the dough out of the mixing bowl, and kneading the color in by hand on a lightly floured surface to distribute the color evenly without over mixing it in the bowl.)
Divide the dough and then press the dough into a disc. Wrap each disc in plastic wrap and refrigerate for at least an hour.
Remove the dough from the fridge, and roll to 1/4-inch thick on a lightly floured surface. (Add flour to the dough, rolling surface, and rolling pin as needed to prevent sticking.) Use a 2-inch circular cookie cutter to cut out 24 rounds from each half of the dough. You'll need to ball up and re-roll the dough to max out the number of cookies you get.
Place the cookies on the prepared baking sheet. Bake for 9 to 12 minutes, or until the cookies are set.
Remove from the oven and cool on the pan for 5 minutes. Transfer cookies to a wire rack and cool completely.
Place the white chocolate in a microwave safe bowl. Heat for 30 seconds and then stir. Repeat heating for 30 seconds and stirring until the chocolate is melted. DO NOT overheat the chocolate! Allow to the chocolate to cool.
Add the butter, powdered sugar, vanilla, and salt to a large mixing bowl. Beat ingredients together until smooth. Add the chocolate and mix until smooth. Scrape the sides of the bowl as needed.
Spread a heaping teaspoon of frosting on the top side of each cookie. Sprinkle with peppermint candy.
If you want to have a little fun, frost the bottom side of half the cookies. Place a second cookie on top of the frosting (bottom side down) and gently press until the frosting reaches the edge of the cookies. Roll the frosting edges in chopped peppermint candy. Makes 2 dozen sandwich cookies.Sugar Cookie recipe adapted from Cake Central