Orange Sauce for Roast Duck

An uncooked sweet-sharp sauce, closer to a Cumberland sauce than to the reduced bigarade most cooks now associate with duck. The whole thing comes together in a bowl and only needs warming.

• Do not let it boilHeat it gently, just until steaming, and take it off. Sustained heat drives off the volatile oils in the orange rind and the bite in the horseradish, leaving a sauce that tastes only of sugar and acid.
• Powdered sugarIn American books of this period "powdered sugar" may mean either a fine-ground granulated sugar or what is now sold as confectioners' or icing sugar; the terms were not used consistently. If you use granulated, whisk over low heat until it is fully dissolved.
• Sweetness is high by current tasteA full cup of sugar to a little over half a cup of juice is very sweet even for a fruit sauce with rich meat. Half to two-thirds of that quantity, added in stages and tasted, may suit current palates better.
• HorseradishThe original means fresh root, grated fine. Bottled prepared horseradish works, but drain off the vinegar first and start with two teaspoons, since jarred products vary widely in strength.
• Currant jellyRed currant jelly, not black currant preserve. It is there for tartness and gloss as much as sweetness; a good tart cranberry jelly is the nearest common substitute.
• Zest before juicingGrate the rind from the orange while it is whole and firm, taking only the coloured layer. The white pith underneath is bitter and there is no cooking step here to soften it.
• Consistency and yieldThis is a pourable sauce, not a glaze; it will look thin in the pan. Six servings works out to two or three tablespoons each.