Preheat the oven to 190ºc/170ºc fan
Add the banana, butter and sugar to a bowl and mix
Add in the egg yolk and vanilla and beat again
Add in the flour, bicarb, salt and cinnamon and beat
Add in the chocolate and mix
Use a 5cm scoop to portion the cookies
Place onto lined trays
Bake the cookies in the oven for 10-12 minutes.
Leave to cool for 30 minutes
