6-8 medium-sized potatoes, peeled
1 onion, peeled
1 egg, beaten
2 tablespoons plain flour
Sea salt and freshly ground black pepper
Oil for shallow frying
For the mushroom sauce
1 onion, peeled, finely chopped
250g chestnut mushrooms
125ml/½ cup vegetable stock
125ml/½ cup double or heavy cream
1 tablespoon sour cream
Extra sour cream to serve
Fresh dill to garnish