8 oz (200-225 g) prepared spinach leaves (net weight)
1 large shallot
2oz (50 g) butter
2oz (60g) cooked ham, very finely chopped
9 fl oz (250 ml) milk
scant 2oz (45 g) plain flour
1 tsp cream of tartar
2oz (60g) grated Emmenthal or Gruyere cheese
2 tbsp fine dry breadcrumbs or grated Parmesan cheese
salt and pepper
Have the mousseline sauce ready prepared. Preheat the oven to 400 Â°F (200 Â°C) mark 6. Wash the spinach thoroughly, drain briefly and cook in a covered pan with no added water for a few minutes until wilted and tender. Drain off any liquid and when cool enough to handle squeeze tightly to eliminate all excess moisture. Chop very finely.
Fry the finely chopped shallot in 1/2. oz (15 g) butter, stirring, for 2-3 minutes then add the ham and fry for a further 2-3 minutes. Add the chopped spinach, sprinkle with a small pinch of salt and cook, stirring, until all the excess moisture has evaporated. Remove from the heat.
Make the white sauce basis for the souffle: heat the milk slowly; melt 1 oz (30 g) butter in a fairly small saucepan, stir in the flour and cook, continuing to stir, for 2-3 minutes over a low heat. Draw aside from the heat, add all the boiling milk at once, beating vigorously as you do so with a balloon whisk or hand-held electric beater to prevent lumps forming. Return to a slightly higher heat and keep stirring as the mixture comes to a gentle boil; simmer and stir until very thick.
Take off the heat, stir in a little salt and freshly ground white pepper and a pinch of nutmeg to taste. Separate the egg whites carefully from the yolks, lightly beat the latter in a small bowl and beat a little at a time into the hot sauce, then stir in the spinach mixture. You can prepare the souffle up to this point several hours in advance but it is slightly easier to fold into the egg whites when freshly made and still warm. Cover the sauce to prevent a skin forming. Before you are ready to proceed to the next stage of the souffle, have the mousseline sauce ready and keep hot over simmering water; preheat the oven. Beat the 4 egg whites with 1 extra egg white until just frothy; add the cream of tartar; this will stabilize the protein and keep the egg whites stiff for longer.
Beat until very stiff but do not overbeat (when they would look dry or ‘grainy). Fold about a quarter of the egg whites into the spinach mixture, together with all but 1 tbsp of the finely grated Gruyere or Emmenthal. Fold this mixture gently but thoroughly into the remaining egg whites.
Grease a 2-pint (1.2-litre) souffle dish with butter, sprinkle with the grated Parmesan cheese or very fine dry breadcrumbs and pour the mixture into it. Tap the bottom on the work surface to settle and level the surface, sprinkle with the remaining cheese, place in the oven, close the oven door and immediately turn down the temperature dial to 375 Â°F (190 Â°C) mark 5 and bake for 25-30 minutes or until the souffle has risen up well in the dish and is a good deep golden brown on top. Serve at once with the mousseline sauce.