Preheat oven to 180* C (360* F) Fan.
Mash the bananas in a bowl with a fork, until pureed.
Add the milk, vanilla and honey. Mix.
Add the oats, walnuts, salt, cinnamon, baking powder and lemon zest.
Stir until all of the ingredients are completely combined and the mixture comes together.
Transfer to a 20x30 cm baking pan that has been brushed with olive oil.
Spread evenly and set it aside to rest for 30 minutes.
Refrigerate for 12-24 hours, until the oats soak up all of the mixture’s liquid.
Bake for 35-45 minutes.
When ready, remove from oven and allow to cool for 15 minutes.
Turn out of pan and cut in to pieces.
Serve with extra honey and fresh fruit.