Cook potatoes, then peel and still hot are crushed with a fork or passed through a press. To tepid mashed add grated yolk of a hard-boiled egg, chopped onion and parsley and vegetable oil. The mixture is stirred well and season to taste with salt, pepper and lemon juice (or vinegar dissolved tartaric acid), then stir, pour into bowl for serving and garnish with olives and slices of hard boiled egg white.