Preheat the oven to 160C(320F) fan-forced and grease and line a round 20cm cake tin.
Place the bananas, dates and vanilla essence in the bowl of the Thermomix (or in a food processor) and mix for 5 seconds on speed 4 (or until smooth). Set aside.
Add the butter and caster sugar and mix for 20 seconds on speed 5 (or in a food processor until smooth).
Add the eggs one at a time and combine each for a few seconds on speed 5 (or until combined).
Add the banana mixture and cinnamon, and mix for 3 seconds on speed 5.
Add the flour, bicarbonate of soda, baking powder, and milk and mix for 15 seconds on speed 4 to 5.
Pour into a lined 20cm cake tin and bake in the oven for 1 hour.
To make the icing, place all the ingredients in the bowl of a Thermomix or food processor and process until smooth. Taste and add a little extra maple syrup if required.