Heat the olive oil, blend in the flour and cook for a few moments.
Add the potatoes. Allow to cook for a few minutes, turning frequently. Season with the salt and pepper, garlic, parsley and nutmeg and just cover with water.
Bring to the boil and allow to simmer very gently. Do not allow the potatoes to break or disintegrate. When cooked, after about 20 minutes, remove from the heat and add the lemon juice and the egg. Mix carefully, then turn out onto a dish, adding a little more parsley if you wish. Serve at once.