4 onions, sliced thinly
150g/5陆oz frozen baby pearl onions
6 large potatoes, peeled and sliced thinly
450ml/16fl oz chicken or lamb stock
500ml/18fl oz chicken stock
salt and freshly ground black pepper
50ml/1戮fl oz olive oil
50驳/1戮辞锄 butter, softened
50g/2oz butter
2.7kg/6lb leg of lamb, bone in
250g/9oz frozen peas