Mash half the avocado with a fork and set aside for now. Then chop the dark chocolate. Preheat the oven to 180 ° C and prepare a small tray (mine is 16 x 26 cm and was enough).
Mix the mashed avocado and oil in a bowl until smooth. Add the flour, cocoa powder, the two types of sugar, baking soda, salt, water and vinegar and stir again until the dough is smooth. Finally add the chocolate pieces.
Pour the dough into the prepared tray and spread it on until the dough is halfway smooth and fills everything. Then bake for 15 to 20 minutes (after 15 minutes, stick a toothpick in and see how sticky the dough is. It shouldn`t be too sticky, but definitely not dry).