Hygienic Cream Sauce

A thin pouring custard thickened with buckwheat rather than wheat flour or cornstarch, meant to be ladled over steamed and baked puddings. It is unsweetened as written, which is deliberate but worth knowing before you pour it.

• Half a pintIn US measure a half pint is one cup, so this is about 1 cup milk and 1 cup cream, making roughly 2 cups of sauce. (If the book is working in imperial measure, a half pint is 10 fl oz and the quantities are correspondingly larger.) The recipe gives no yield.
• Buckwheat means the flourNot groats or kasha. Use buckwheat flour, slaked smooth in a tablespoon or two of cold milk before it goes near the hot pan; a tablespoon of it is a light thickening that gives a pourable sauce, not a set custard.
• A well-lined saucepanThe period phrase most likely means a pan with an intact lining, typically tin over copper, so the milk never touched bare metal. Any heavy-bottomed stainless or enamelled pan does the job now; the point is even heat, since milk and cream scorch fast.
• The five-minute boilThe recipe says to boil it five minutes; a bare simmer with constant stirring is safer for milk and cream. The extended cooking is what takes the raw taste off the buckwheat.
• Adding the yolkOff the heat, and temper it — beat a few spoonfuls of the hot sauce into the diluted yolk first, then return the lot to the pan. Dropped straight in, the yolk scrambles into threads. If you want the yolk properly cooked, set the pan back over low heat and stir until the sauce reaches 170F, stopping well short of a boil.
• No sugar, no flavouringThe recipe gives none, in keeping with the "hygienic" label. For most puddings you will want 2 to 3 tablespoons of sugar dissolved in the milk, and vanilla or a little nutmeg stirred in at the end.
• ServingIt thickens noticeably as it cools. Serve warm, and thin with a spoonful of milk if it has stood.