Preheat oven to 325 degrees. Stir in stock, tomatoes, star anise, cinnamon sticks, carrots, remaining 2 teaspoons cumin, 2 teaspoons coriander, 1 tablespoon ginger, remaining 1 teaspoon salt, and reserved lamb. Bring to a boil, reduce heat to medium, and simmer, stirring occasionally, uncovered, for about 1 hour, until lamb is tender and sauce is thick.