1 kg (2.2 pounds) potatoes, a mix of waxy and baking potatoes (if you prefer to use only one type, pick waxy potatoes, not too firm)
500 ml (2 cups) milk (whole or part-skim, not skim)
1 1/2 teaspoons salt
Freshly grated nutmeg
1 clove garlic, sliced lengthwise
3 tablespoons finely chopped chives (optional)
60 ml (1/4 cup) heavy cream
2/3 cup grated Parmesan, Gruyere and/or Swiss Cheese
Wash, peel and slice potatoes thinly. A mandolin would come in handy. Do not wash them after or you will lose that precious starch.
Combine the sliced potatoes, milk, salt and a good grating of nutmeg in a saucepan. Bring to a simmer over medium-low heat, and keep simmering for 8 minutes, stirring the potatoes and scraping the bottom of the pan regularly to prevent sticking/scorching. The milk will gradually thicken to a creamy consistency.
While the potatoes are simmering, preheat the oven to 220°C (430°F) and rub the bottom and sides of a medium earthenware or glass baking dish (I use an oval dish that's 26 cm/10 inches at its widest, and 2 liters/2 quarts in capacity) with the cut sides of the garlic clove.
Transfer half of the potatoes into the baking dish, sprinkle with the chives if using, drizzle with half of the cream and sprinkle half the cheese onto the middle layer. Add the rest of the potatoes, pour the cooking milk over them, and drizzle with the remaining cream. Sprinkle top with remaining cheese.
Bake for 35 to 40 minutes, until bubbly on the edges and nicely browned at the top. Let stand for 5 minutes before serving.