Thinly slice the onion and begin browning it with the oil in a saucepan over medium heat. When onion pieces start to soften, add chana masala and coriander powder. Stir until thoroughly mixed. Add rinsed and drained chickpeas and scallions (chopped green onion) and heat for ~5 more minutes.
While the chickpea mixture is cooking, heat the water to just less than boiling, then add couscous. When all the water has absorbed, take chickpeas off heat, add couscous, and stir.