Soak the chickpeas for 8 to 12 hours in cool water. After soaking, rinse (do not collect soaking water), cover with water and bring to a boil. Simmer for about 1½ hours or until the chickpeas are tender. Drain and let cool. Put in a large salad bowl.
Cut the brocoli into small bunches. Slice celery and green onions. Add the vegetables and pumpkin seeds to the salad bowl.
In a small bowl, add all the ingredients of the vinaigrette and whisk for a few moments with a fork.
