In a medium bowl, whisk together the flour, cocoa powder, espresso powder, baking powder, and salt. Set aside.

In a large bowl using a handheld or a stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium-high speed until smooth and creamy, about 3 minutes. Add the egg and vanilla and beat on medium-high speed until combined, about 1 minute. Scrape down the sides and bottom of the bowl and beat again as needed to combine.

Add the dry ingredients to the wet ingredients and mix on low speed until combined. The dough will be soft and sticky. Cover the bowl tightly and refrigerate for at least 1 hour and up to 2 days.

Line large baking sheets with parchment paper or silicone baking mats. Scoop a heaping Tablespoon (about 30g) of chilled cookie dough per cookie and roll into balls. Arrange dough balls 3 inches apart on the prepared baking sheets. Place the cookie stamp directly on top of each cookie dough ball, centering it as best as you can, then firmly press down until the dough extends nearly to the edges of the cookie stamp. Lift straight up. If your cookie dough is sticking to the cookie stamp, use a pastry brush to lightly brush cocoa powder on the stamp before stamping the cookie dough ball. You can then brush the excess cocoa powder off the tops of the stamped cookies, if desired.

Chill the stamped cookies in the refrigerator for 1 hour before baking to set the shape.

Preheat the oven to 350°F (177°C) for even baking.

Bake the cookies for 10-12 minutes, or until the edges are set.

Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.