Cook couscous according to package directions. Meanwhile, in a microwave-safe bowl, cook the broccoli, carrots and water on high for 1 minute; drain. Transfer to a large bowl. Add the couscous and onions.
Combine the vinegar, oil, sugar, ginger and salt; pour over couscous mixture and stir gently to coat. Stir in cashews and garbanzo beans. Gently fold in feta if desired.