In a large skillet, saute onion, apple, garlic, and curry powder in margarine u ntil tender. Remove skillet from heat and blend in flour, salt, cardamom, and poepper. Stir in chicken broth and lime juice until curry sauce is well blended. Bring curry sauce to a boil, reduce heat, and simmer, uncovered for about 5 min utes. Stir occasionally. Meanwhile, place scallops or shirmp in a pot of boiling water and cook until ju st tender 5-10 minutes. Drain and set aside. When curry sauce is finished cooking, add shellfish and mushrooms and serve ove r rice.