In a large bowl, beat butter and sugar together, add the egg yolks.
Combine flour and cocoa powder in a separate bowl. Add salt. Add the flour mixture slowly to the first bowl, using a mixer.
Once the dough is thoroughly mixed and there are no lumps, knead the dough into a ball. Cover with plastic wrap and place in the fridge for at least 45 minutes and up to overnight.
When ready to make cookies remove dough from the fridge. Preheat the air fryer to 300 degrees F, air fryer setting. Roll out the dough on a very lightly floured surface. Using a round, circular cookie cutter, cut out cookies.
Line basket with parchment paper and place cookies in the basket, leaving a half-inch of space between each cookie—air fry cookies for about 7 minutes. Remove cookies from the air fryer and allow them to cool on the cookie rack.
Once cookies are completely cool, melt white chocolate according to directions on the package, stir well, add peppermint extract, & stir again. Dip each cookie halfway into the white chocolate and then into the peppermint candy pieces and set on parchment paper to dry.
Plate, serve, and enjoy!