Sift 50 g (2 oz) of the flour and salt into a bowl. Break in the egg. Gradually add 150 ml (1/4 pint) milk, beating to form a smooth batter. Stir in the spinach.

Heat a little butter in a 20.5 cm (8 inch) frying pan. When hot pour in 45 ml (3 tbsp) batter, tilting pan to cover base. Cook until the pancake moves freely, turn, cook until golden. Make 4 pancakes.

Put the remaining butter, flour and milk in a saucepan. Heat, whisking continuously, until the sauce thickens, boils and is smooth. Stir in the lemon rind, bay leaf and fish. Cook for 6 minutes.

Divide the mixture equally between the pancakes, then roll up. Serve hot with a green salad.