1 head broccoli, cut into florets
1 large cauliflower, cut into florets
1 pack baby leeks (approx. 150g/5½oz), sliced
6 tbsp fresh breadcrumbs
4 tbsp flour
50g/1¾oz butter, plus extra for cooking the leeks
200g/7oz mature cheddar, grated
500ml/18fl oz milk