Preheat the oven to 190°C and spray an oven dish or roasting tin with low-calorie cooking spray.
In a small bowl, combine the harissa paste, pomegranate juice and tomato purée. Leave to one side.
Score the surface of the chicken breasts diagonally. Add the onion, peppers and chicken to the oven dish or tray.
Pour over the harissa mixture, coating the chicken breasts well. Cover with foil and pop into the oven for 15 minutes. Remove the foil and cook for a further 20-25 minutes. The chicken should be cooked through with softened vegetables just starting to brown around the edges.
Add the couscous to a bowl and pour over the boiling water. Cover and leave to stand for 5 minutes.
Add the pomegranate seeds and mint. Season to taste with salt and pepper.
In a small bowl, add the yoghurt, harissa and honey and mix well. Leave until ready to serve.
Remove the tray from the oven. Serve alongside the couscous. Drizzle over the yoghurt and sprinkle over the remaining pomegranate seeds.