Heat butter in tight, fully covered saucepan. Add onion and garlic, cook over low heat for 5 minutes. Add tomatoes and juice and bring to a boil. Sprinkle rice on top of tomatoes. Add salt, pepper cayenne and soup mix. Cook for 15 minutes. Then add green pepper, celery, parsley and basil. If necessary, add a little water or tomatoe juice and cook for another 5 minutes. Transfer to a casserole dish and add shrimp, chicken and juices, sliced mushrooms. Cover tightly. Bake in preheated oven for 15 minutes 350 degrees F till shrimp are cooked, but not overdone.