Preheat oven to 350 degrees. Line two baking sheets with parchment paper and set aside.
Add flour, baking powder and salt to a medium sized bowl and whisk to combine. Set aside.
Add softened butter and granulated white sugar to a large bowl. Cream together with an electric mixer for two minutes.
Then add in an egg, peppermint extract and vanilla, and mix until pale in color and fluffy, about 1 minute.
Add in the dry ingredients and mix until combined.
Scoop the dough into 36 portions and roll into balls. (If the dough is too soft, chill it for 5-10 minutes until easier to work with.)
Transfer the balls to the parchment paper lined baking sheets, two inches apart. Slightly flatten each.
Bake the cookies for 9-11 minutes. Let the cookies cool for a few minutes after baking, then transfer them to a cooling rack to completely cool.