Whisk cocoa, 3/4 cup granulated sugar, and oil evenly. Beat in eggs individually, then vanilla.
Whisk flour, baking powder, and salt; fold into chocolate mixture. Cover; refrigerate 2 hours until scoopable, additional to listed active time.
Heat oven to 350°F; parchment-line two sheets. Form 24 balls; roll in coating granulated sugar, then thickly in powdered sugar.
Bake one sheet at a time 10 to 11 minutes until tops crack, rims firm, and centers soft.
Cool on sheets 5 minutes; rack-cool completely before stacking.