Wash rice in three changes of hot water. Add to 1-1/2 cup water in saucepan, heat to boiling. Cover and lower heat; simmer 30-45 minutes. Saute onions and mushrooms in butter until onion is transparent, 3-5 minutes. Add flour and stir, cooking for 5 minutes. Stir in chicken broth and bring to boil. Stir until smooth and flour is thoroughly cooked. Add cream or half & half and sherry. Stir until heated through, but do not allow to boil.