Preheat the oven to 180°C/160°C Fan/Gas Mark 4. Grease and line a 20cm square tin or a 23cm round cake tin.

To make the cake, chop the watercress until very fine – ideally do this in a blender. Put it in a mixing bowl with the rest of the cake ingredients and beat until well incorporated. Try not to over stir – it isn’t the end of the world if you do, but the cake may not rise as well as it could.

Pour the batter into the prepared cake tin and bake in the preheated oven for approximately 50-60 minutes. The cake is done when a skewer inserted in the centre comes out clean. Set the cake aside to rest for 15 minutes before removing it from the tin. Leave on a cooling rack until cold.

To make the frosting, beat the butter and icing sugar together until pale in colour then gently fold in the cream cheese until evenly mixed.

Spread a lovely thick layer of cream cheese frosting over the top of the cake and decorate with a few edible flowers, such as violas or rose petals to make a real showstopper.