In a medium bowl whisk together flour, cocoa, baking powder and salt. Set aside.
In a mixer beat both sugars, eggs and vanilla on high speed until light and airy. Add melted butter and beat until well combined. Gradually add flour mixture and mix well. The batter will be a similar consistency to brownie batter.
Cover batter with plastic wrap and refrigerate for two hours to firm up.
Preheat oven to 350 F. Line insulated baking sheets with parchment paper.
From the dough, make one-inch balls and roll in powdered sugar. Place on baking sheet 2 inches apart. Bake for 10 minutes. Do not over bake. They will appear a bit glossy on top, so don't be tempted to bake much longer.
Remove from oven and cool on pan 4-5 minutes then carefully transfer cookies to cooling rack to cool completely. Cookies will be chewy.
Be sure to place cookies 2-inches apart on baking sheets as they double in size while baking.
Let the cookies rest and cool so they will set up. Otherwise they may fall apart when you pick them up warm.