Courgette and banana sheet cake with caramel buttercream

Courgette and banana create magic together in this cake! Complete with a generous layer of caramel buttercream icing, you'll definitely be going back for seconds of this delicious concoction.

By Sophie Gray
  • 10 mins preparation
  • 35 mins cooking
  • Makes 16
  • Print


  • 115 g butter at room temperature
  • 1 cup sugar
  • 1/2 cup brown sugar
  • 1 cup mashed ripe banana (approx 2 medium-sized)
  • 1/3 cup yoghurt (see notes)
  • 1 egg
  • 2 tsp vanilla extract
  • 3 loose cups grated courgette (approx 2 medium-sized), squeezed of excess juice
  • 2 tbsp milk
  • 1 tsp baking soda
  • 2 cups plain flour
  • 1 tsp baking powder
  • pinch of salt
  • 1 tsp mixed spice
  • 1/2 tsp cinnamon
Caramel buttercream icing
  • 100 g butter, at room temperature
  • 2 1/2 cups icing sugar
  • 3 tbsp caramel
  • 1 tbsp milk, if needed


  • 1
    Preheat oven to 180°C. Grease and line a 23cm x 33cm Swiss roll pan. In a bowl or food processor, beat the butter and sugars. Add the mashed banana, yoghurt, egg and vanilla and mix lightly. Stir in the grated courgette.
  • 2
    Bring the milk to the boil in a small pan or microwave, stir in the baking soda to dissolve. Add to courgette mixture. Sift in the flour, baking powder, salt and spices and mix to combine.
  • 3
    Spread in the prepared pan. Bake for 35-37 minutes, or until a skewer inserted in the center comes out clean. Remove and let cool completely.
  • 4
    Meanwhile, make the Caramel buttercream icing (see below), and spread on cake when cake has cooled.
Caramel buttercream icing
  • 5
    Beat butter and icing sugar at a low speed until combined, then increase speed and beat for 6-8 minutes until pale. Add caramel and beat, adding the milk gradually if needed.
  • 6
    If you want to amp up the caramel icing to the next level, warm another 2 tablespoons of caramel in the microwave, stir until smooth and splatter it over the icing. Add a pinch of flaky sea salt if you like a hint of salted caramel.


1 medium banana yields about ½ a cup when mashed. You can use a flavoured yoghurt or natural, or swap the yoghurt for buttermilk, or the same amount of milk soured with a drop of lemon juice.