Heat 1 tablespoon oil in a saucepan over medium heat. Add onion and garlic, then cook, stirring, for 3-4 minutes until softened. Stir in red peppers and chicken, then cook for 10 minutes or until chicken is golden.
Combine the harissa and 150ml water in a small bowl, then stir into the chicken mixture. Bring to a simmer over medium-high heat, then reduce heat to medium-low and cook, covered, for 30 minutes. Remove chicken. Pour liquid into a blender and blend until smooth, then return to the pan with chicken. Cook over low heat for a further 10-15 minutes until sauce is slightly thickened.
Meanwhile, cook couscous according to the packet instructions. Fluff with a fork, then season and set aside.
Heat remaining 2 teaspoons oil in a frypan over medium heat. Add chickpeas and cook, stirring, for 2 minutes or until golden. Add cinnamon and cumin, then season and cook for 1 minute or until fragrant. Add lemon juice and couscous, and toss to combine, then cook for 2 minutes or until heated through. Transfer to a serving bowl and sprinkle with almonds and parsley, then serve with chicken.