1. Drop the potatoes into enough lightly salted boiling water to cover them completely and cook briskly until they show no resistance when pierced with the point of a small, sharp knife. Drain and return the potatoes to the pan. Shake the pan constantly over moderate heat for a minute or so until the potatoes are completely dry. Then mash them to a smooth puree.

2. With a large mortar and pestle or the back of a spoon, mash the garlic and salt together to a fine paste. Add the warm mashed potatoes a little at a time, stirring and mashing vigorously until the ingredients are well combined.

3. Beat in the egg yolk, then the oil, a tablespoon or so at a time, making sure each addition of oil is absorbed before adding more. The mixture will absorb from 8 to 12 tablespoons of oil, depending on the texture of the potatoes.

4. Beat in the lemon juice, taste and add as much pepper and salt as you think it needs. The sauce should be highly seasoned and dense enough to hold its shape almost solidly in a spoon. If you prefer a thinner sauce, beat in a little lukewarm water a few drops at a time. Skordalia is traditionally served with fried food or broiled seafood or with cold sliced beets.