Although it may sound like a bizarre juxtaposition, the combination of apple purée and mayonnaise makes an excellent sauce for cold meats, especially pork and game. It is best to use sour baking apples (Reinettes de Canada are among the best), but if they cannot be found, Granny Smiths will produce a very satisfactory sauce. Prepare the apple purée by first peeling, coring, and slicing the apples. Coat the sliced apples with a few drops of lemon juice to prevent them from turning brown, as well as to add a note of acidity to the finished sauce. (Never soak sliced apples in water, or their natural sugars and flavor will leach out.) Cook the apples gently in a covered saucepan with 1 tablespoon (15 milliliters) white wine. (Use this amount of wine regardless of how many apples you use.) This may seem like a small amount of liquid, but remember that the apples themselves will release liquid as soon as they are heated by the steaming wine. As soon as the apples are soft, usually after about 10 minutes, purée them in a food processor or food mill, or through a drum sieve. Return the purée to the saucepan and reduce it until it is stiff and no liquid remains. Be careful to stir the mixture constantly with a wooden spoon and not allow it to burn. Allow to cool before incorporating into the mayonnaise.
The proportion of apple purée to mayonnaise will vary depending on the apples’ flavor; anywhere from one part apple purée and three parts basic mayonnaise to equal parts of each will work. One pound (450 grams)—about 2 large apples—provides approximately 1 cup (250 milliliters) purée. Flavor the apple mayonnaise with grated horseradish, about 1 tablespoon (15 milliliters) per cup (250 milliliters).