Whisk cocoa, 3/4 cup granulated sugar and oil until evenly combined. Beat in eggs one at a time, then vanilla.
Whisk flour, baking powder and salt and fold into the chocolate mixture. Cover and refrigerate for 2 hours, additional to the listed active time, until scoopable.
Heat the oven to 350°F and line two sheets with parchment. Divide into 24 balls and roll each in the coating granulated sugar, then thickly in powdered sugar.
Bake one sheet at a time for 10 to 11 minutes, until the tops crack and the rims are firm while the middles remain soft.
Cool on the sheets for 5 minutes, then transfer to racks and let cool completely before stacking.