Using a large mixing bowl, cream together butter, sugar and cocoa powder.
Add 1 egg at a time beating until batter is well combined. Add vanilla extract.
Combine the flour, baking powder and salt. Whisk to combine.
Add the dry ingredients to the wet ingredients and mix until the flour mix is well incorporated and smooth.
Cover the dough with plastic wrap and chill overnight. This step is super important! It makes the dough easy to roll out and helps the cookies keep their shape during baking.
Once you're ready to bake the cookies, preheat your oven to 350° degrees F.
Line two baking sheets with parchment paper.
Pour granulated sugar and powdered sugar into two separate small bowls.
Using a tablespoon, scoop the chilled dough and roll into 1" balls. Roll into granulated sugar and then into powdered sugar. The granulated sugar helps create a crisp crust on the cookie and also helps the powdered sugar stick better.
Place cookies 3x4 on a baking sheet. Bake 11-12 minutes or until the edges of the cookies are firm and centers are puffy. The center may still look a little wet, but the cookies will continue to bake after removing from the oven. The cookies will have a crisp outer crust, and a soft, fudgy molten center.
Allow cookies to set and cool for 5 minutes before transferring to a cooling rack.
