In a large bowl, using a hand-held mixer or stand mixer with a paddle attachment, cream butter and sugar for 3-4 minutes, until the mixture is light and fluffy. Add the egg and mix well. Mix in sour cream, peppermint and vanilla extracts, beating just until combined.

In a separate bowl, stir together flour, baking powder and salt. Gradually add flour mixture to butter mixture, mixing just until flour is incorporated and the dough is smooth and soft. Place dough in a Rubbermaid TakeAlongs Deep Square and refrigerate for at least one hour.

After refrigeration, preheat oven to 350 degrees Line two baking sheets with parchment paper. Set aside.

To make cutout cookies, dust counter with flour and roll the dough to desired thickness about ¼-inch. Using a cookie cutter, cut the dough into desired shapes. Place the cookies on prepared baking sheets. Bake for 8-10 minutes, being careful not to over bake. Allow cookies to cool on baking sheet for 1-2 minutes before transferring them to a wire rack to cool completely before frosting and decorating.

While cookies are cooling, prepare buttercream frosting. In a large bowl, using a hand-held mixer or stand mixer with a paddle attachment, beat butter until creamy. Beat in peppermint extract. Slowly add the powdered sugar one cup at a time alternating with the milk, mixing until desired consistency is reached. Stir in red food coloring, if using. Fill piping bag with prepared frosting and pipe frosting onto cooled cookies. Alternatively, frosting can be spread onto cookies with a knife or offset spatula. Top frosting with crushed peppermint candies.