Sauce Mousseline is a light version of Hollandaise Sauce.

1 3/4 pounds frozen spinach
6 tablespoons heavy cream
1 egg yolk
4 tablespoons fresh bread crumbs
pinch grated nutmeg
salt and pepper
1 pound store-bought puff pastry, defrosted if necessary
4-5 tablespoons semolina
1 x 4- to 5-pound salmon, filleted and skinned
1 egg, beaten

Hollandaise Sauce
2 tablespoons lemon juice
4 black peppercorns
3 egg yolks
3/4 cup butter, cubed
salt and pepper
2/3 cup heavy cream, whipped

Preheat the oven to 425°F. Cools the spinach following the directions on the package. Drain well, squeezing out as much water as possible. Puree in a blender or food processor, then place in a bowl and stir in the cream, egg yolk and bread crumbs. Season with nutmeg and salt and pepper.

Divide the pastry dough in half and roll out one half very thinly into a large rectangle. Trim, so that the pastry measures 1 1/2 inches larger all around than a fillet. Place the pastry on a baking sheet and prick all over with a fork. Bake for 20 minutes, turning it over half way through. Keep the oven on.

Remove the pastry from the oven and turn it over again. Cool slightly. Dredge with the semolina. Lay one salmon fillet on top, spread with the spinach and lay the other fillet on top, turned head to tail.

Roll out the remaining pastry into a large rectangle measuring 1 1/2 inches larger than the base all around. Brush the edges with beaten egg and cover the salmon, tucking in the edges underneath. Use a teaspoon to make scales and use the pastry trimmings to make leaves. Make 4 small slits in the top and brush all over with egg. Bake for 25 minutes, then reduce the temperature to 350°F for a further 25 minutes longer.

Meanwhile, make the sauce.

Put the lemon juice, peppercorns and 2 tablespoons water into a small pan. Boil to reduce to 1 tablespoon liquid. Put the egg yolks into a bowl. Strain the reduced liquid over them, then place the bowl over a pan of just-simmering water. Beat the mixture together, then beat in the butter, cube by cube, beating constantly. Keep the sauce warm, but not hot, and if it overheats and starts to separate, remove the bowl from the pan and plunge the bottom into a bowl of cold water. Beat until the sauce is smooth, then return the bowl to the pan and continue. When all the butter has been amalgamated, season to taste. Stir the cream into the Hollandaise. Adjust the seasoning and dilute if necessary, with a little more lemon juice. Serve the salmon very hot with the sauce.

SERVES 8-10