While couscous is cooking, prepare dressing by combining all ingredients and whisking thoroughly.
After couscous has rested, drain any remaining water (if any), add cooked garbanzo beans and toss with dressing. Let cool.
Add nectarines, parsley and scallions. Toss well and chill 1 hour.
Place garbanzo beans in a bowl, cover with water by about 2 inches and soak overnight in the refrigerator.
Drain and rinse garbanzo beans. Place in a pot with 4 cups of water. Bring to a boil, reduce heat and simmer until soft, about 2 hours. Drain and let cool while preparing the remaining ingredients.
Bring the remaining 1-1/4 cups water to a boil. Add couscous and bring to a boil. Cover and reduce heat to a simmer. Cook until all water has been absorbed, about 20 minutes. Remove from heat and keep covered for 5 minutes.
Pearl Couscous Salad with Garbanzos and Nectarines