1. Soak beans overnight or place in covered pot of boiling water, removed from heat.
2. Cook beans in 6- to 8-quart pot, with water to cover, for 1 hour.
3. In medium saucepan, sauté onions and carrots in oil until soft. Add to pot of beans. Add potato, garlic, salt, pepper, and bay leaf.
4. Cook another 30 to 45 minutes or until beans are soft. Remove bay leaf.
5. Puree one-half to three-fourths of soup, and then remix with remainder of soup. Add spinach and mix gently.