1. Whisk together first 5 ingredients in a bowl until combined well. Pour half of marinade in a glass pie plate or dish just large enough to hold salmon, reserving remaining marinade.
2. Preheat grill. Put salmon in dish and turn to coat. Let fish marinate, turning occasionally, at room temperature for 20 minutes.
3. Grill fish, skin-side up, on a lightly oiled rack over moderate heat, uncovered. Turn once until golden brown and just cooked through, for 10 to 12 minutes total. Grill green onions, laying them crosswise on a lightly oiled rack. season with salt and pepper to taste and grill, turning once, until just tender, about 3 minutes.
4. Meanwhile, bring remaining marinade to a boil in a small saucepan and simmer 1 minute. Serve salmon over green onions drizzled with sauce. Makes 4 servings.