Wash the potatoes, peel them and slice them on the mandolin (2-3 mm thick), sprinkle with (plenty!) Coarse sea salt and rub, then leave to rest for at least 10 minutes. Warm the cream double and milk, season with pepper and nutmeg. Squeeze the potatoes flat with your hands and add to the milk, bring to the boil and cook for about 3 minutes, stirring again and again. Remove from heat and mix in 150 g of cheese.