For the chocolate muffins, preheat the oven to 150 °C convection. Mix the flour, cocoa powder, sugar, baking powder and baking soda, then add the oil, milk and egg and mix well.
For the chocolate chips, chop the chocolate not too small. Either in a food processor or with a sharp knife.
Add the chocolate chips to the rest of the mixture and mix again. Pour the mixture into muffin cups and bake at 150 °C for 18-22 minutes.