Put the potatoes unpeeled in a big pot. Add water until the potatoes are covered and boil for 45 minutes. Remove the potatoes from the heat, let them cool, remove their skin and mash them thoroughly.
Mash the garlic in a bowl and add some salt. Add the mashed garlic to the mashed potatoes and mix them well. Add the egg yolk. Finally, add the oil, the vinegar, the lemon juice and mix them all together well.
Put the mixture in the refrigerator for 10 minutes and serve.
