1. Heat the oven to 220oC, Fan 200°C, Gas 7. Cut the peppers into 3cm chunks and place in a large roasting tin, add the onion, garlic, olive oil, chilli, a good pinch of salt and pepper, then toss together until everything is coated in oil. Roast for 20 minutes or until lightly charred around the edges.
2. Remove the garlic cloves, place on a board and work to a puree with the blade of a knife. Stir into the passata then return to the oven for a further 10 minutes. Adjust the season to taste.
To serve: cook potato quarters according to instructions - allow 4-5 per person - and portion into heatproof dishes. Top with a portion of firecracker peppers, then scatter 20g grated mozzarella over each. Reheat in the oven until piping hot and the cheese has melted. Sprinkle with coriander or chives and serve with a side of soured cream.