Preheat oven to 350º and line baking sheets with parchment paper.
Whisk flour, baking powder and salt together in a bowl.
In an electric mixer, beat butter and sugar on medium until fluffy, 3-6 minutes. Add eggs, one at a t time, and vanilla and beat until combined. Reduce speed to low, slowly add flour mixture, and beat until combined. If your dough is too sticky to work with, refrigerate briefly.
Using a 2 tablespoon ice-cream scoop, roll dough into balls with slightly wet hands. Roll in about 1/2 cup of sugar and place on the prepared cookie sheet. Using a buttered and sugared bottom of a flat bottomed drinking glass, flatten each ball to about 3/4 inch thickness. Sprinkle with crushed peppermint candies.
Bake for 10-12 minutes, until edges are set and beginning to brown but centers are still soft and puffy. Let cool on sheet for 10 minutes and then transfer to a wire rack.
America’s Test Kitchen – Best-Ever Christmas Cookies 2015