Prep: Preheat the oven to 375 degrees F and line two baking sheets with parchment paper, then set them aside.
Crush the peppermint candies in a ziplocked bag, using a rolling pin or meat tenderizer.
Dough: In a large bowl, using an electric mixer, cream the butter and sugar. Beat in the egg yolks and then add the flour.
Add the crushed peppermint candies and the mint extract, stir to combine.
Roll the dough out into 1-inch sized balls, then roll each ball in granulated sugar. Place the cookie dough on the prepared baking sheets 2-inches apart. Use the back of a teaspoon measuring spoon to create a small well in the center of each dough ball.
Bake: Place the cookies in the preheated oven and bake for 8-10 minutes.
Let them cool on the baking sheet for a couple of minutes before transferring them to a rack to cool completely. If needed, use the teaspoon to press the center of each cookie again to form the well before the cookies cool.
Fudge Filling: Combine the heavy cream, butter, and chocolate chips in a small saucepan. Stir over low heat until the mixture has melted and then let it cool.
Once the fudge has cooled and thickened, use your teaspoon to scoop the fudge and fill the center of each cookie. Top with a sprinkle of peppermint candies. Serve and enjoy!