Wash rice and soak, if recommended on package. Melt butter in large saucepan. Add carrots, celery and green onion, and saute' 3 or 4 minutes. Add water, bouillon cubes, salt, and drained rice. Bring to a boil and simmer, covered, until rice is tender and water is absorbed (about 40 minutes). (Add more water if needed to cook rice.) Add crawfish tails and stir until blended.
Preheat oven to 375 degrees F. Mix soup, sherry, butter, and seasonings in a double boiler. Heat thoroughly. If sauce gets too thick, add more sherry. Mix 2/3 of sauce with rice mixture and pour into a butter 2-2 1/2-quart casserole. Bake 30 minutes. Serve remaining sauce separately. Serves 8-10. (Lobster tails may be substituted for the crawfish. Follow package instructions on frozen lobster tails for cooking.)
Tomatoes stuffed with equal parts seasoned dry bread crumbs and Parmesan cheese, dotted with butter, may be slipped into the oven along with this dish, for an excellent meal.