Cream Sauce

A hot foamy pudding sauce in the sabayon family, thickened by air rather than starch or yolk. The whole thing hangs on pouring the cream onto the whites in a thin stream while whisking, so the foam warms without collapsing or scrambling.

• The cream measure2/3 pint is roughly 1 1/3 to 1 2/3 cups, depending on whether an American (16 fl oz) or British (20 fl oz) pint is meant. Use heavy or whipping cream; the sauce has no other thickener and light cream will stay thin.
• "Set in stewpan boiling water"This is a double boiler: the pan of cream sits in a larger pan of simmering water. It is there to hold the cream just at the boil without scorching the milk solids on the base.
• Sugar quantityNo amount is given. For this volume of cream, 2 to 3 tablespoons of caster or granulated sugar suits most steamed and baked puddings; add it to the hot cream so it dissolves completely before the whites go in.
• The pourWhip the whites to soft, glossy peaks in a warmed bowl, then add the hot cream in a slow thread while whisking constantly. Tipping it in at once will deflate the foam and can set the egg into threads.
• Vanilla lastExtract goes in off the heat, as the original has it. Alcohol-based vanilla loses much of its aroma if it is boiled with the cream.
• Egg safetyThe whites are warmed by the cream but never cooked through. If the sauce is for anyone very young, elderly, pregnant or immune-compromised, use pasteurised whites.
• Serve at onceYield is roughly 2 cups. The foam starts to weep fairly quickly, so make it while the pudding is turning out rather than in advance.