In a large skillet, heat oil over medium heat; saute onion and garlic with curry powder until tender, 3-4 minutes. Stir in tomatoes, chickpeas, sweet potato, coconut milk, sugar and pepper flakes; bring to a boil. Reduce heat; simmer, uncovered, until mixture is thickened and potatoes are tender, 25-30 minutes, stirring occasionally.
Meanwhile, prepare couscous and peas separately according to package directions. Stir salt into peas.
To serve, divide couscous among 6 bowls. Top with chickpea mixture, peas, parsley and, if desired, yogurt.
