Preheat the oven to 350ºF. Put the softened butter and sugar in a large bowl. Use a hand mixer to blend together until smooth.
Add the egg, vanilla extract, and peppermint extract then blend on HIGH until it turns fluffy.
In another bowl whisk together the flour, cocoa powder, baking powder, and salt.
Add the wet mix to the dry mix. Use a hand mixer to blend together. As you mix, slowly drizzle in the milk until it all comes together.
Stir in the chocolate chips and stir. Cover with plastic wrap and place into the fridge to cool for 30 minutes.
Line a baking sheet with parchment paper. Use a cookie scoop to measure out the cookies on the sheet, spreading them out to allow for expansion during baking. Bake for 10–15 minutes.
Remove from the oven and let cool. In the meantime, melt the white chocolate. Once the cookies have cooled, decorate with the white chocolate. I alternate between dipping them in the chocolate and drizzling the chocolate over them. Once done, stick the crushed candy into the wet chocolate.