Line an 8 or 9 inch square pan with parchment paper.

Into a bowl, sift the flour, powdered sugar and cocoa. Add the salt and brown sugar then whisk the mixture.

Add the avocado oil and the vanilla and switch to a rubber spatula. Mix until the dough is fully combined and there are no streaks or bits of flour.

Press the dough into the pan, using the back of a measuring cup or the spatula to pack it in and smooth over the top.

Preheat the oven to 350 F (the dough should wait 15 minutes before baking it). Sprinkle the top with flaky sea salt.

Bake the cookies for 20 minutes then remove from the oven.

Line a greased cookie sheet with parchment paper. Use the parchment sling to remove the cookie from the pan.

Slice the cookie in half, then each half in half, and then again so you have eight thin columns. Now slice them into thirds so you have 24 finger long cookies.

Use a fish spatula (or something very thin that can slide under the cookies) to transfer the cookies one by one onto the cookie sheet. Leave some space between each cookie, at least half an inch.

Return to the oven for another 10 minutes.

Once the cookies are cool you can store them in an airtight container. They’ll keep for a week.