Heat the oil in a large wide heavy pot over medium heat. Add the onions and cook until they start to brown, 10 to 15 minutes. Add the cumin, garlic, ginger, cardamom, cloves, cinnamon and star anise, and cook, stirring often, 1 to 2 minutes. Add the curry powder and some chili powder (if you want it spicy) and cook for another minute. Stir in the chicken, coating well with the spices, and cook for about 2 minutes. Add the cilantro, salt, tomatoes, potatoes and curry leaves. Simmer until the chicken is cooked through, about 30 minutes. Add additional seasoning, if necessary.
Dig out the center of each bread loaf half in one piece, reserving the "plug". Spoon the curry into the hollow of each loaf half and place the plug on top. Serve with carrot salad. Using your hands, break off some of the bread and use it to scoop up some curry and the carrot salad.