Don’t be perturbed by the savoury ingredient in these cakes, because it is truly magical: the courgettes release all of their water, leaving a very moist, spongy cupcake. I recommend baking them in heavily buttered muffin tins or silicone moulds; baker Julia Aden recently recommended putting a round piece of greaseproof paper in the base of each mould to help remove small cakes, and it works a treat.