Melt chocolate in a microwave safe bowl on 50% powder. Stir until smooth. Set aside.
To prepare dough: In a medium size mixing bowl use a whisk to sift together flour, cocoa powder, baking powder, espresso and salt.
Using an electric mixer, cream together butter, 1/2 cup granulated and brown sugar in a large bowl. Add vanilla and melted chocolate. Beat until fully combined.
Add eggs one at a time beating well after each addition. Stop and scrape the bowl occasionally.
Lower the speed of the mixer and gradually add sifted dry ingredients beating just until fully moistened. The cookie dough will be thick. Cover and chill for 2 hours or overnight.
To bake: Preheat oven to 350°F. Line 2 baking sheets with parchment paper.
Divide dough into approximately 1 1/2 tablespoons. Roll into a ball. Roll ball first in granulated sugar then powdered sugar. Place 2 inches apart on baking sheet.
Bake for 10 -12 minutes. Cool on pan for 3 minutes then remove to a cooling rack to cool completely.
Store in an airtight container at room temperature for up to 3 days.