Place cocoa, sugar, salt, EVOO, eggs and vanilla into the Thermomix bowl and blend 10 sec/speed 8.
Scrape down the lid and sides of bowl and add the flour and baking powder. Blend 5 sec/speed 5. Finish combining by hand with a spatula.
Scrape the mixture into a bowl and cover with something airtight. Refrigerate for at least 4 hours, longer is fine. (It can stand 24 hours in the fridge and in fact becomes easier to work with the colder it gets.
When you are ready to bake, preheat the oven to 180°C fan forced and line two baking trays with paper.
Place the icing sugar into a small bowl. Using wet hands, form small walnut size balls of dough and toss in the icing sugar, coating generously. Place onto the prepared trays with space between them for spreading.
Bake 12-14 minutes, they will still be soft when you take them out of the oven. Cool on the tray for 10 minutes before moving them to a cooling rack. Store in an airtight container and keeping them in the fridge is entirely ok.