2 tablespoons olive oil
1-1/2 cups chopped onion
8 garlic cloves, chopped
1/4 cup chopped jalapeños with seeds (optional)
2 cups dried beans (black or other), soaked for a couple hours and drained
1 tablespoon ground cumin
2 teaspoons ground coriander
8 cups (or more) chicken or vegetable stock
1 cup coarsely chopped fresh cilantro
Lime wedges

Heat oil in heavy large pot over medium-high heat. Add onion, garlic and optional jalapeños; sauté 5 minutes. Mix in beans and spices. Add 8 cups stock and bring to boil. Reduce heat, cover and simmer until beans are tender, stirring occasionally, about 1-2 hours. Working in batches, puree soup with cilantro in blender (or in pot with an immersion blender). Season to taste with salt and pepper. Bring soup to simmer, thinning with more stock if necessary. Ladle into bowls. Serve, passing lime wedges separately.  (Can be prepared 1 day ahead).

– http://www.epicurious.com