Preparation Heat oil in a 4-to 5-quart heavy pot over medium-high heat until it shimmers, then sauté onion, garlic, and jalapeño with chili powder, cumin, oregano, and 1/2 teaspoon salt until onion is beginning to brown, 6 to 8 minutes. Add beans, water, and bay leaf and simmer, covered, stirring occasionally, until soup has thickened slightly, about 15 minutes. Transfer about 2 cups soup to a blender and purée (use caution when blending hot liquids). Return to pot and reheat over medium-low heat, stirring frequently. Discard bay leaf. Season with salt.
Preparation Heat oil in a 4-to 5-quart heavy pot over medium-high heat until it shimmers, then sauté onion, garlic, and jalapeño with chili powder, cumin, oregano, and 1/2 teaspoon salt until onion is beginning to brown, 6 to 8 minutes. Add beans, water, and bay leaf and simmer, covered, stirring occasionally, until soup has thickened slightly, about 15 minutes. Transfer about 2 cups soup to a blender and purée (use caution when blending hot liquids). Return to pot and reheat over medium-low heat, stirring frequently. Discard bay leaf. Season with salt.