Heat oven to 180C/160C fan/gas 4. Butter and line a 20 x 30cm baking tin with two strips of criss-crossed baking parchment. In a jug, mash the bananas with a fork, then add the butter and sugar and mix with an electric whisk until smooth and creamy.

Add the eggs one at a time, beating well after each addition, then add the vanilla and a pinch of salt. Use a spatula to fold through the flour, yogurt and chocolate chunks. Scrape the mixture into the tin and smooth over the surface. Bake for 30 mins until risen and golden and a skewer inserted into the centre of the cake comes out clean. Cool for 10 mins in the tin, then transfer to a wire rack.

Cut the traybake into 12 squares, then top each one with a spoonful of caramel and a banana chip, if you like. Will keep in a tin for up to five days, or in the freezer – without the toppings – for up to a month.