1 large leek, very thinly sliced
1kg/2lb 4oz potatoes, peeled, cut into cubes and boiled
salt and freshly ground black pepper
1 tsp dried mixed herbs
150g/5陆oz mature cheddar, grated
100驳/3陆辞锄 cream cheese
150ml/5fl oz full-fat milk, plus 1 tbsp for brushing
320驳/11陆辞锄 puff pastry sheet
freshly cooked frozen peas, to serve