In a large mixing bowl or the bowl of a stand mixer, whip the butter and sugars on medium-high speed until light and fluffy. Mix in the egg, followed by the vanilla bean paste and the coffee.

In a separate bowl, sieve the flour, cocoa powder, baking soda, and salt. Add dry mixture to the butter bowl, and mix on low speed until well-combined.

Stir in the chopped dark chocolate and the Milk Duds, reserving a few pieces of each to press into the tops of the cookies.

Cover dough with clingfilm/plastic wrap and transfer to the refrigerator to chill, at least one hour.

Preheat oven to 350° F / 175° C. Line two baking trays with silicone baking mats, and set aside until ready to use.

Remove cookie dough from refrigerator. Use a cookie scoop to scoop chilled dough into fifteen portions, rolling each into a ball.

Place dough balls on prepared trays, allowing a good amount of space in between. Use the palm of your hand to flatten each ball slightly, pressing a few additional Milk Duds into the top of each cookie.

Transfer trays to the freezer and freeze for 10 minutes.

Bake cookies in preheated oven for about 12-14 minutes. Do not overbake.

Allow cookies to cool completely before removing from the tray.

Store leftovers in an airtight container at room temperature for up to five days.