Mix the yogurt and harissa paste together. Add the fish to the mixture and make sure each piece is fully coated. Leave in the fridge.
Preheat the oven to 200°C/fan 180°C/gas mark 6. In a large roasting dish, toss the peppers, onions and tomatoes in the garlic, oil and bay leaves. Roast for about 15mins – or until the peppers are soft.
Nestle the fish into the roasting vegetables and cook for a further 15 minutes. Add a bit more of the yogurt and harrisa marinade to the fish if you like extra heat.
Microwave the grain pouch for 2 minutes and serve with the fish and vegetables. Garnish with the basil leaves.