Portion the chicken fillet, tenderize it lightly and season it with salt and white pepper. Roll each piece in flour and fry until golden in preheated oil.
Fry the remaining flour for 3-4 minutes in the melted butter and dilute the sauce with the cream and half the milk. Allow the sauce to come to a boil, stirring it constantly, remove it from the heat and add the grated roquefort cheese.
Stir and sprinkle it with the remaining white pepper. Peel the potatoes, cut them and boil them in a pot with the lid on, without salt.
Drain and puree them with remaining butter, salt to taste and remaining milk, until you get a smooth puree. Serve each chicken serving with roquefort sauce with a side of mashed potatoes or sauteed vegetables.