Soak navy beans overnight. Drain them and place in large soup pot with onions, leek, carrots, and garlic. Add water to an inch above the level of the beans. Bring them to a boil and then simmer, covered, until tender (about 1 1/2 hours). Mix in the salt, pepper, and paprika. Ladle out 2 cups of the hot bean water and slowly stir it into the flour until smooth. Add the flour mixture to the beans, stirring constantly. Remove the soup from the heat and whisk in the sour cream and then the vinegar. Gently reheat the soup for about 10 minutes. Recipe By :