Penne and Broad Bean Gratin

The broad beans add a wonderful zap to this pasta gratin, while the flavoured mascarpone cream helps to keep everything really moist. This dish can be prepared several hours in advance and just popped into a preheated oven at 180°C (350°F/gas mark 4) for 25–30 minutes or until heated through, and then flashed under the grill until bubbling.