Liquid Sauce

A pudding sauce of the plainest sort — flour-thickened sugar syrup enriched with creamed butter. The whole thing turns on keeping the heat low once the butter goes in.

• Do not boil after the butterWhipping half a cup of creamed butter into a hot flour syrup makes a loose emulsion. Held at a bare simmer it stays glossy; brought back to a boil it may break and weep fat. "Cook slowly for some time" is best read as the lowest heat you have, with no bubbling; the recipe sets no time.
• Mix flour and sugar dry firstThe dry sugar keeps the flour particles apart so the boiling water does not lump them. Add the water in a thin stream while whisking.
• "Beaten to a cream"Softened butter beaten pale and fluffy, as for hard sauce — not melted. Take it out of the refrigerator an hour ahead.
• NutmegWhole nutmeg grated to order was common in household kitchens, and is markedly stronger and less dusty than pre-ground, though ground nutmeg was also sold. If you grate it yourself, start with a little less.
• Vanilla and lemon"A little" is left to the cook; a small quantity of each is enough. Note that the recipe adds them before the final slow cooking rather than off the heat.
• Yield and servingMakes roughly two cups -- enough for six to eight servings of steamed pudding, gingerbread, apple dumplings or cottage pudding. Serve warm; it thickens as it cools and can be gently rewarmed without boiling.