1 1/2pounds boneless sirloin or beef tenderloin, trimmed, and cut in 1-inch cubes
2bunches green onions, white and light green parts only, trimmed in 1-inch lengths
1/8teaspoon coarse salt
2teaspoons peanut oil, plus additional for grill
8-- (10-inch) bamboo skewers, soaked in water at least 30 minutes
Bring soy sauce, mirin, sugar and vinegar to a boil in a small, heavy saucepan. Reduce heat, and simmer 5 to 7 minutes, until slightly syrupy.
Toss beef cubes with 1 teaspoon oil in a small bowl. Toss green onions with remaining 1 teaspoon oil and salt in a second bowl. Thread beef and onions onto skewers, using 3 onion sections between each piece of beef.
Prepare a grill or heat a grill pan to medium-high. Lightly oil. Grill skewers 1 minute, turn, and grill 1 minute on second side. Brush with glaze, grill 1 minute more, turning, and brushing skewers with additional glaze. Transfer to a serving platter, and brush lightly with glaze again.