01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
02 - In a small bowl, dissolve the instant espresso powder in the hot water. Set aside to cool slightly.
03 - In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt.
04 - In a large bowl, cream the softened butter and sugar together until light and fluffy, about 3 minutes.
05 - Beat in the egg, then add the dissolved espresso and vanilla extract, mixing until well combined.
06 - Gradually add the dry ingredients to the wet mixture, mixing just until a soft dough forms.
07 - Scoop tablespoon-sized portions of dough and roll into balls. Roll each ball in the extra granulated sugar to coat.
08 - Arrange the dough balls 2 inches apart on the prepared baking sheets. Gently flatten each ball with the bottom of a glass.
09 - Bake for 9 to 11 minutes, until the edges are set and the centers look slightly underbaked.
10 - Let the cookies cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.