Preheat your oven to 350°F and line a baking sheet (or two) with parchment paper.
In a large bowl, sift in the cocoa powder. Add the white sugar and olive oil and whisk or stir to combine; set aside.
In a small bowl, add the plant-based milk and cornstarch and whisk together until no lumps remain. Add this to the chocolate sugar mixture and stir.
Stir in the vanilla extract, baking powder, baking soda, and salt. Finally, stir in the flour.
Add 1/2 cup of white sugar to a small bowl and 1/2 cup of powdered sugar to another small bowl.
Scoop 1.5 Tbsp dough balls onto your prepared baking sheet – I bake 8 at a time. Roll each dough ball smooth, and then wash the chocolate off your hands.
Roll each dough ball in the granulated sugar and then in the powdered sugar (I like a heavy coating of powdered sugar just on the tops and sides) and place them back on the baking sheet. I like to gently re-shape them a bit at this step if they look wonky.
Bake at 350°F for 8-10 minutes. The cookies should spread and have cracks. If desired, as soon as you pull the cookies out the oven, you can use the back of a small spoon to gently push in any cookie edges that aren’t totally round.
Allow the cookies to set on the baking sheet for 2 minutes before transferring to a cooling rack.
Repeat steps 6-8 until all cookies are baked.
Store cooled cookies in an airtight container at room temperature with a piece of parchment paper between layers.