Step 1

Beat together cocoa powder, white sugar, vegetable oil: In the bowl of an electric mixer fitted with the paddle attachment (or beat by hand with a wooden spoon) beat together the cocoa powder, white sugar, and vegetable oil until it comes together into a shiny, gritty, black dough of sorts.

Step 2

Add eggs, one at a time, add vanilla: Add the eggs, one at a time, mixing for 30 seconds each. Add the vanilla and beat in thoroughly.

Step 3

Whisk together flour, baking powder, salt, espresso powder: In a separate bowl, whisk together the flour, baking powder, salt, and espresso powder if using.

Step 4

Beat dry ingredients into cocoa oil mix: Mix into the chocolate mixture on low speed until just combined. Do not over-beat.

Step 5

Cover and chill: Cover the dough with plastic wrap and chill the dough for four hours or overnight.

Step 6

Get ready for baking: Preheat the oven to 350°F and line two baking sheets with parchment paper. Place the powdered sugar in a wide bowl.

Step 7

Roll the cookies: Using a rounded teaspoon, scoop out clumps of the chilled dough and roll them into 1-inch (2.5 cm) sized balls using your hands. Do several at a time and drop them into the powdered sugar as you go. The dough will be quite sticky, so it's useful to roll the dough in batches.Roll the balls in the powdered sugar and place on the cookie sheets spaced a few inches apart. (You should be able to get 12 to 16 on each sheet).

Step 8

Bake: Bake at 350°F for 10 to 13 minutes. Allow to cool a minute or two on the sheets before transferring to a wire rack to cool completely. Repeat with any remaining batter.

Step 9

Store: Store these cookies in an airtight container on the counter. They will keep for at least a week before starting to become crumbly and dry.