2 Tbs. vegetable oil
2 medium yellow onions, chopped
3 medium cloves garlic, coarsely chopped
1-1/2 tsp. ground coriander
1 tsp. ground cumin
1/4 tsp. aniseed
Freshly ground black pepper
2 quarts lower-salt chicken broth or homemade vegetable broth
Four 15.5-oz. or two 29-oz. cans black beans, rinsed and drained
2 medium sweet potatoes, peeled and cut into medium dice
Kosher salt
1/2 cup plain yogurt
8 paper-thin lime slices