Sift the 90 g (3 oz) flour into a bowl, whisk the eggs into the flour gradually, until the mixture is smooth. Stir in the water and oil and leave the batter to stand for 30 minutes.

Heat a frying pan and brush it lightly with the melted butter. Put 1 tablespoon of the batter in the centre and roll and tilt the pan to coat the base evenly.

Fry until the pancake is golden brown underneath, then carefully turn over, to brown the other side. Stack and keep warm until required. Repeat until all the batter has been used up.

Melt the 2 tbsps of butter in a saucepan and stir in the 2 tablespoons of flour. Gradually add the milk, beating well, and returning the pan to the heat between additions, until all the milk has been incorporated. Simmer the sauce for 2-3 minutes. Stir in the lemon juice and season to taste.

Mix together half of the sauce and the prawns. Put one pancake into an ovenproof dish and spread a spoonful of the prawn sauce over this. Cover with another pancake and repeat the sauce/pancake procedure until all the pancakes have been used up, finishing with a pancake. Bake in a preheated oven, 190°C/375°F/Gas Mark 5, for 10 minutes.

Cover with the remaining sauce and garnish with lemon slices. Cut the crespelle like a cake, to serve.