In large pot, heat oil over medium heat. Add onions; sauté 2 minutes. Add zucchini and salt; sauté 5 minutes longer. Add stock; cover and bring to a boil. Reduce heat; simmer 15 minutes or until vegetables are tender. Remove from heat; stir in soymilk, soy sauce, nutmeg and pepper. Cool 15 minutes. In batches, process zucchini mixture in blender container until smooth; pour into clean container. Refrigerate, covered, 4 hours or until thoroughly chilled. Garnish individual servings with chives.