1/4 cup rice wine vinegar
2 tablespoons brown sugar
1/4 cup soy sauce
1 tablespoon fresh ginger root, coating scraped off with the tip of a spoon and finely minced
2 tablespoons sliced scallions, white and tender green parts only (1 or 2 scallions)
1/4 cup cornstarch dissolved in 1/4 cup water
2 pounds boneless chicken breasts, cut into cubes
Salt and freshly ground black pepper
1 cup sake
12 bamboo skewers
2 leeks, white parts only, soaked in salt water to remove grit and sliced on the bias into 1-inch lengths