Soak beans overnight in 2 quarts water. (Alternatively, place beans and 2 quarts water in a large pot. Bring to a boil. Boil for 2 minutes. Remove from heat and let stand for 1 hour.) Drain the beans, discarding soaking liquid.

Combine oil, mustard seeds, chili powder, cumin and cardamom in a 5- to 6-quart Dutch oven. Place over high heat and stir until the spices sizzle, about 30 seconds. Add onions, mushrooms, tomatillos and water. Cover and cook, stirring occasionally, until the vegetables are juicy, 5 to 7 minutes. Uncover and stir often until the juices evaporate and the vegetables are lightly browned, 10 to 15 minutes. Add broth, tomato paste and chipotles; mix well.

Place the beans in a 5- to 6-quart slow cooker. Pour the hot vegetable mixture over the beans. Turn heat to high. Put the lid on and cook until the beans are creamy, 5 to 8 hours.

Garnish each serving with cheese, a dollop of sour cream and a sprinkling of cilantro. Serve with lime wedges. Stovetop Variation: Total: 4 1/2 hours In Step 2, increase broth to 81/2 cups. Omit Step 3. Add the beans to the Dutch oven; cover and simmer the chili gently over low heat, stirring occasionally, until the beans are creamy to bite, about 3 hours.

Ingredient notes: Chipotle peppers are dried, smoked jalapeno peppers. Ground chipotle chile pepper can be found in the specialty spice section of most supermarkets. Chipotle chiles in adobo sauce are smoked jalapenos packed in a flavorful sauce. Look for the small cans with the Mexican foods in large supermarkets. Once opened, they'll keep up to 2 weeks in the refrigerator or 6 months in the freezer.

Tomatillos are tart, plum-size green fruits that look like small, husk-covered green tomatoes. Find them in the produce section near the tomatoes. Remove the outer husk and rinse them well before using.

MAKE AHEAD TIP: Cover and refrigerate for up to 2 days or freeze for up to 3 months.

Equipment: 5- to 6-quart slow cooker