Pre heat oven to 180 C and put 12 muffin cases (reusable ones if possible) into a 12 hole muffin tin
Peel and mash the bananas with a fork in a mixing bowl until no lumps remain.
Add the yoghurt, maple syrup, milk and vanilla extract to the bowl until combined.
In a separate bowl sift the flour, cocoa powder, bicarbonate of soda, baking powder, cinnamon and salt.
Chop up the chocolate into chunks.
Add the flour and coaca mixture and chocolate chunks to the wet ingredients to form a batter.
Add equal amounts of better into the muffin cases.
Bake in the oven for 20-25 minutes.
Leave to cool on a cooling rack.
Store in an airtight container.