Start by washing the sliced leek in warm water, then drain well. Put the leek and the butter in a large frying pan over a medium heat and soften for 2 minutes. Remove to a plate. Wipe out the pan with some kitchen paper.
In a large mixing bowl combine the egg, olive oil, baking powder, gram flour, sweetcorn, chives, grated courgette and the softened leek. Mix well, then season. The moisture from the courgette and leeks, along with the egg, should provide enough liquid to bind the mixture, but if it is still stiff, add a splash of milk. You want it to be loose enough to drop easily from a spoon.
Pour in enough oil to cover the base of the frying pan and place over a medium heat. Spoon a heaped tablespoon of mixture into the hot oil
and, if necessary, gently flatten out the mound slightly so the fritter is approximately 1cm thick. Cook for 2-3 minutes on each side until golden. If the fritters are browning too quickly, turn the heat down.
As the fritters are ready, place on kitchen paper to absorb any excess oil and sprinkle with a little sea salt. Keep warm. Repeat until you have used up all the mixture. Serve the fritters with a spoonful of rose harissa pesto on the side, a few fresh herbs and, if you like, any of the optional serving suggestions.