1-Preheat the oven to 350℉ (177℃): Preheat the oven to 350℉ (177℃). Line baking sheet pans with silicone baking mats or parchment paper.
2-In a medium bowl, whisk together the: In a medium bowl, whisk together the all-purpose flour, dark cocoa powder, instant espresso powder, and salt. Set aside.
3-In the bowl of a stand mixer: In the bowl of a stand mixer fitted with a paddle attachment or in a large bowl with an electric hand mixer, cream the unsalted butter and granulated sugar until light and creamy. Add in the egg yolks, milk, and vanilla extract and mix to combine. Add in the flour mixture and mix on low speed until the cookie dough comes together.
4-Portion the cookie dough using a small: Portion the cookie dough using a small cookie scoop (1 tablespoon). Roll the dough into a ball and then roll the ball in holiday nonpareil sprinkles. Place the cookie dough balls onto the prepared cookie sheet pan. Bake the cookies for about 10 minutes.
5-Remove the pan from the oven: Remove the pan from the oven. Immediately press a Hershey’s kiss in the center of each cookie. Cool the cookies on the pan for 2 minutes and then transfer to a wire rack to cool completely.