To make the filling, put the haddock fillets in a large pan. Add the milk and poach for 6-8 minutes, until just tender. Lift out the fish using a draining spoon and, when cool enough to handle, remove skin and bones. Reserve the milk. Measure the single cream into a jug, then strain enough milk into the jug to make it up to 450ml/2/3 pint .

Melt the butter in a pan, stir in the flour and cook gently for 1 minute. Gradually mix in the milk mixture, stirring continuously to make a smooth sauce. Cook for 2-3 minutes. Season to taste with salt, pepper and nutmeg. Flake the haddock and fold into the sauce with the eggs. Leave to cool.

Preheat the oven to 180C. Divide the filling among the pancakes. Fold the sides of each pancake into the centre, then roll them up to enclose the filling completely.

Butter four or six individual ovenproof dishes and arrange two or three filled pancakes in each, or butter one large dish for all the pancakes. Brush with melted butter and cook for 15 minutes. Sprinkle over the Gruyere and cook for a further 5 minutes, until warmed through. Serve hot wit a few curly salad leaves, if you wish.