- Preheat the oven to 425°F. Lightly grease (or line with parchment) two baking sheets.
- Melt the butter in a microwave-safe bowl, add the sugar, and return to the microwave for 30 to 45 seconds, until the mixture is hot to the touch.
- Beat in the vanilla, baking powder, salt, espresso powder, and egg. Cool to lukewarm.
- Add the flour and chocolate chunks, stirring briefly, just until well-combined.
- Drop the dough by tablespoonfuls onto the prepared baking sheets.
- Bake the cookies for 9 minutes, until they're barely set. Remove them from the oven, and cool right on the pan.
- Store in a cookie jar for up to a week.