Wash fillets, coated them with sunflower oil, add salt lightly as the salt pulls the water from the fish and can make it dry and put on the BBQ. While they bake their mess sauce - put vinegar in the pot, chopped onion, pepper and coffee spoon salt. Let boil until the vinegar has evaporated, add the egg yolks and milk, which have been at room temperature and stirring until we get light cream. Get out of the heat and add the butter, which is soft and melted again at room temperature and lemon juice. Blend and serve.