Black Bean Soup Recipe
Boston Cooking School, 1880s

1 pint black beans
2 quarts cold water
1 small onion
2 teaspoons salt
2 teaspoons pepper
1/2 teaspoon cayenne
2 teaspoons mustard
1 tablespoon flour
2 tablespoons butter
1 lemon
2 hard-boiled eggs

Soak the beans overnight. In the morning pour off the water, and put them on to boil in two quarts of cold water. Slice the onion and fry it in one tablespoon of butter. Put it with the beans. Add a bit of celery root, if you have it. Simmer four or five hours, or until the beans are soft. Add more cold water as it boils away, about half a cup every half-hour, to check the boiling and soften the beans. Leave about two quarts of water when done. Rub the beans through a strainer, put the soup on to boil again, and add the salt, pepper, and mustard. When boiling, thicken it with flour and butter which have been cooked together. This will prevent the beans from settling. Season to taste. Cut the lemon and eggs into thin slices, put them into the tureen (bowl), and pour hot soup over them. Serve with croutons.

Many think tomatoes are an improvement. If that flavor is desired, add to the above a half a can of tomatoes, before straining.