Potato Soup
Boil 4 good sized potatoes in salted water until tender but unbroken. In the meantime scald together 1 quart of milk, 2 slices of onion, 6 peppercorns and either a stalk of celery or a sprig of parsley. Cook for ten minutes, draw back and drop in 1 scant tablespoonful of butter rubbed to a paste with I large tablespoonful of flour. Stir gently until this is dissolved and the liquid thickened. Press the potatoes through a ricer directly into the milk, add salt to taste, stir and cook for ten minutes. Rub through a sieve.
If too thick thin with a little hot milk. Reheat and it is ready to serve.
A straightforward milk-thickened potato purée. The only real technical hazard is scorching the milk, and the only real judgment call is final consistency.
- Scald, don't boil"Scald" means bringing the milk to just below the boil, around 180F, when it steams and shows bubbles at the edge. Use a heavy pan over medium-low heat and stir; milk with flour in it catches on the bottom quickly and a scorched note carries through the whole pot.
- Strain the aromaticsThe onion slices, peppercorns and celery or parsley are there for flavour, not texture. The recipe does not say to remove them, and the final rubbing through a sieve would catch them, but lifting or straining them out before the butter-and-flour paste goes in makes the later sieving easier.
- Beurre manié, not rouxButter "rubbed to a paste" with flour is beurre manié, worked in raw off the heat. Draw the pan back as directed, whisk it in in small pinches, then return to low heat for a couple of minutes so the flour loses its raw taste.
- QuantitiesFour good-sized potatoes is roughly 1 1/2 lb; a floury variety such as russet gives the cleanest purée. One quart of milk is 4 cups. The recipe specifies only 'milk'; skim will taste thin.
- Ricer before sieveRiced potato goes into hot milk without lumping, which is the point of ricing directly into the pan. Never use a food processor or blender on cooked potato -- it develops the starch and turns the soup gluey.
- The final sievePressing the finished soup through a fine sieve is what separates this from mashed potato in milk. Push it through with the back of a ladle; it takes a few minutes and is worth doing.
- YieldAbout 6 cups, serving four as a first course. It thickens noticeably as it stands and on reheating, so keep hot milk to hand.
Potato soup earns its place in a low-cost cookery book by arithmetic: a pound and a half of potatoes, a quart of milk and a spoonful of butter feed four people, and the flavour comes from onion, peppercorns and a stalk of celery that cost almost nothing. The method itself resembles what is often described as the standard cream-soup formula of the period -- scalded milk infused with aromatics, thickened with butter and flour, then combined with a sieved vegetable. The insistence on ricing and then sieving reflects a period taste for smoothness in soups, achieved by hand labour before there was any machine to do it, and the potatoes are directed to be boiled "tender but unbroken".