Melt butter in heavy 2- to 3-quart saucepan.
Add scallions and toss about 30 seconds.
Remove and set aside.
Add water and salt to pan and bring to boil.
Stir in rice.
Reduce heat, cover and simmer 20 minutes.
Remove from heat and let stand covered 5 minutes.
Fluff with fork (if rice is too moist, cover with several paper towels).
Reheat gently if needed and then toss with reserved scallions and parsley.
Mound in lettuce cups and serve immediately