Packaged mixes of dried beans can be found in specialty and health food stores. Or just combine a number of types of dried beans yourself—the actual number of different kinds is not all that important.
2 medium-large red or yellow onions, chopped
4carrots, trimmed, peeled, and sliced
4garlic cloves, thinly sliced
4teaspoonspaprika, preferably Hungarian
1 small dried hot chili or apinch of dried red pepper flakes
½pound dried mixed beans, soaked overnight in enough cold water to cover by 2inches and drained (or use quick-soak method, Dried Bean Basics)
3cupsreduced-sodium chicken broth or vegetable broth
2tablespoons chopped fresh parsley
1tablespoonbalsamic vinegar or red wine vinegar, or to taste
Salt and freshly ground black pepper, to taste
4scallions (white and green portions), trimmed and thinly sliced on a sharp diagonal
Combine the onions, oil, and about 1 tablespoon of water in a nonreactive large, wide nonstick saucepan; cook over low heat until the onions are softened, about 5 minutes. Add the carrots and garlic; cook, stirring, until the carrots soften, about 5 minutes. Stir in the paprika, marjoram, and hot chili pepper; cook, stirring, for 1 minute longer. Add the tomato paste, drained soaked beans, chicken broth, and 6 cups of water. Bring to a boil. Skim the foam off the top with a skimmer or large metal spoon. Partially cover the pan, lower the heat, and simmer the soup until the beans are quite tender, about 1½ hours.
Stir in the parsley, vinegar, and salt and pepper. Taste and correct the seasonings, adding more vinegar, spices, and herbs, if desired. Remove the hot chili. Serve, sprinkled with scallions.