1 pound dried black beans (2 1/2 cups), picked over and rinsed
1 tablespoon extra-virgin olive oil
1/4 cup mustard seeds
2 tablespoons chili powder
1 1/2 teaspoons cumin seeds or ground cumin
1/2 teaspoon cardamom seeds or ground cardamom
2 medium onions, coarsely chopped
1 pound mushrooms, wiped clean, trimmed and sliced (4 1/2 cups)
8 ounces tomatillos, husked, rinsed and coarsely chopped (see Ingredient Notes)
1/4 cup water
5 1/2 cups mushroom broth or vegetable broth, homemade or canned (see Ingredient Notes)
1 6-ounce can tomato paste
1-2 tablespoons minced canned chipotle peppers in adobo sauce (see Ingredient Notes)
1 1/4 cups grated Monterey Jack or pepper jack cheese
1/2 cup reduced-fat sour cream
1/2 cup chopped fresh cilantro
2 limes, cut into wedges