Sift and sort through the beans and remove any stones and broken beans. In a large pot, place sorted beans and enough water to cover by 3 inches. Do not cover with a lid. Bring the water to a simmer over medium-high heat. Continue simmering for 2 minutes. Remove from heat. Cover and let stand for 1 hour. Drain beans and set aside.

In another large pot, heat oil over medium heat until hot. Add onion and garlic and sauté until onion softens, about 3 minutes. Add jalapeno, chili powder, cumin and oregano and sauté about 5 minutes, or until the jalapeño is soft. Add cooked beans, water, lime juice and bay leaf (if using) and bring to a boil. Reduce heat and simmer, covered, stirring occasionally, until soup thickens, about 15 minutes. Remove the bay leaf.

Transfer 2 cups soup to a blender and purée. Return to pot and reheat over medium-low heat, stirring frequently. Add salt and stir.

Serve topped with a dollop of sour cream, chopped cilantro and chopped tomato for garnish, if desired.