To make the pistou sauce, crush the basil leaves and garlic in a mortle and pestle to make a fine paste. Transfer the paste to a bowl and stir in the grated cheese and lemon rind. Gradually blend in the oil, a little at a time, until combined, then transfer to a serving dish.

To make the fritters, put the grated courgette and finely chopped spinach in a sieve over a bowl and sprinkle with plenty of salt. Leave for 1 hour then rinse thoroughly. Dry well on kitchen paper.

Sift the flour into a bowl and make a well in the centre, then add the egg yolk and oil. Measure 5 tbsp. of water and a little to the bowl.

Whisk the egg yolk and oil, gradually incorporating the flour and water to make a smooth batter, season and set aside for 30min.

Stir the grated and rinsed courgettes and finely chopped and rinsed spinach into the batter. Whisk the egg white until stiff then fold into the batter.

Heat 1cm of oil in a frying pan. Add dessert spoons of batter to the oil and fry for about 2 mins until golden brown and crispy. Remove from the pan, using a slotted spoon. Place the fritters on kitchen paper and keep warm while frying the rest. Serve hot fritters with the pistou sauce.