Beat sugar and oil together with the paddle attachment of a stand mixer until light and fluffy.
Add in eggs and vanilla.
Mix in flour, cocoa, salt, baking powder until combined. Dough will be wet. Cover and chill 4-24 hours.
Preheat oven to 350 degrees F
Form balls of dough, about 1 1/4 inch. Roll to cover completely in powdered sugar.
Place on baking sheet covered with parchment paper, placing cookies 2 inches apart.
BAKE 10-12 minutes or until cookies are set. Err on the side of undercooked. Cool 2 minutes on baking sheet. Remove to wire rack to cool completely.
Notes
This dough is a sticky dough and needs to be refrigerated for at least two hours to prevent the cookies from overspreading.
Use a cookie scoop to get evenly sized cookies. It's important that cookies are the same size so that they bake evenly.
Roll cookie balls into powdered sugar right before baking. The cookie dough will absorb the powdered sugar coating as they sit before going in the oven. A hard shell will form and keep the cookies from spreading and crinkling. Keep remaining cookie dough in the refrigerator until ready to roll into balls and in powdered sugar just before baking.
Err on the side of under cooked with these cookies. Bake them a minute less than you think they need. That way you will have a crisp edge and they will still be nice and chewy in the middle. The middle of the cookie should still look wet when you remove them from the oven. They will set up as they cool.