4 floury potatoes (about 800g/1lb 12oz), peeled and chopped into roughly 2.5cm/1in chunks
2 onions, roughly chopped
small bunch fresh parsley, leaves roughly chopped (optional)
salt and black pepper
1 litre/1戮 pint vegetable stock
60驳/2录辞锄 butter
125ml/4fl oz single cream