Preheat a convection oven to 300 degrees F. Line baking sheets with parchment paper.

In a mixer, blend the butter and sugars until light and fluffy. Add the eggs one at a time and mix well. Add the vanilla extract and mix well.

Meanwhile, sift together the flour, baking powder, baking soda, salt, and espresso powder.

With the mixer running, slowly add the flour mixture until well incorporated. Stop the mixer a couple of times to scrape the sides and bottom of the bowl.

Scoop cookie dough into balls about 1 inch in diameter. Drop a few at a time into the bowl with the sugar-espresso powder mixture; roll them around to coat evenly. Space several inches apart on the baking sheet.

Use the flat bottom of a glass to press the cookie dough balls down to about 1/4" thick. If the dough sticks to the bottom of the glass, dip the glass in the sugar mixture.

Bake for about 16 minutes or until the outside is mostly firm and the inside is still a little soft. Cool on baking sheets for 3-5 minutes; remove from baking sheet and cool completely.

In a medium sized bowl, blend the sugar and espresso powder well.