For the wet ingredients, combine cocoa powder, cane sugar, butter and tahini into a bowl and mix. Add one egg at a time, and mix thoroughly between each egg. Mix in the vanilla extract.

For the dry ingredients, combine whole wheat and oat flour, baking powder and salt into a bowl and mix.

Do not mix in the whole dry mixture into the wet one at once, do it in 2-3 rounds, mixing thoroughly the batter in between. 

Refrigerate the batter for at least 4 hours, or overnight.

Form small balls with the batter and coat them in powdered sugar for the classic crinkle cookie version. Forming them with sightly wet hands helps them not to stick to your hands as much.  Since the cookies themselves are not very sweet, the powdered sugar adds just the right amount of sweetness and balances them out.

Bake them in a preheated oven 180°C/350°F for about 8 minutes, my personal time is 7 minutes 30 seconds, but I will let you experiment with this one, since everyone’s oven is a bit different. Do not leave the batter outside for too long, since it softens and balls are harder to form. 

Another option is to coat them in coconut flakes if you do not want the extra sugar, but as the coconut flakes bake, they turn brown and lose the festive appearance. I coated them in dark chocolate afterwards, and this way, the nice touch of coconut remained + the cookies received a tasty makeover.