01 -
In a medium bowl, whisk together the flour, cocoa powder, instant espresso powder, baking soda, and salt until thoroughly combined.
02 -
In a separate large bowl using an electric mixer or stand mixer fitted with a paddle attachment, beat the butter, granulated sugar, and brown sugar on medium-high speed for 2-3 minutes until light and fluffy.
03 -
Add the egg, vanilla extract, rum extract, and milk to the butter mixture and beat until light and fluffy, 1-2 minutes, scraping down the sides and bottom of the bowl as needed.
04 -
Reduce mixer speed to low and gradually incorporate the dry ingredients into the wet ingredients until just combined.
05 -
Cover dough with plastic wrap and chill for at least 2 hours or up to 3 days. Do not skip this crucial step as it prevents excessive spreading during baking.
06 -
Preheat oven to 350°F (175°C) and line two large baking sheets with parchment paper. If dough has chilled longer than 24 hours, allow it to soften at room temperature for 15-30 minutes for easier scooping.
07 -
Using a medium cookie scoop (approximately 3 tablespoons), portion dough and place 2-3 inches apart on the prepared baking sheets. The dough will be sticky; slightly wet your hands to prevent sticking if needed when shaping.
08 -
Bake in the preheated oven for 10-12 minutes or until edges are set and tops appear slightly soft. Cool cookies for 5 minutes on the baking sheet, then transfer to a wire rack to cool completely.
09 -
While cookies cool, place white chocolate in a microwave-safe container (a tall liquid measuring cup works best). Microwave in 30-second intervals, stirring between each, until completely melted and smooth.
10 -
Dip half of each cooled cookie into the melted white chocolate, then place on parchment paper. Immediately garnish each with 1-3 coffee beans. Allow to set at room temperature or place in freezer briefly to accelerate setting.