Preheat your oven to 160°C (140°C fan). Rub the cut side of the garlic clove all over a medium baking dish, then lightly grease with butter. This infuses subtle garlic flavour into the gratin.

Peel the potatoes and slice them very thinly, about 2 mm thick, using a mandoline or sharp knife. Try to keep the slices even for uniform cooking. Place them in cold water briefly to prevent browning, then pat dry thoroughly before layering.

In a medium saucepan, combine milk, double cream, a pinch of nutmeg, and a little salt and pepper. Warm gently over low heat until just below simmering. Do not let it boil, as this would cause the cream to split.

Arrange a layer of potato slices in the prepared dish, slightly overlapping each piece. Season lightly with salt and pepper, then pour a little of the warm cream mixture over the top. Continue layering and seasoning until all potatoes and cream are used, finishing with a layer of potatoes.

Dot the top with small pieces of butter to encourage browning. Cover loosely with foil and bake for 45 minutes. This gentle start helps the potatoes cook evenly without drying out.

Remove the foil and continue baking for another 30–35 minutes, or until the top turns golden and the cream thickens to a rich, velvety texture. Insert a knife to test doneness; it should slide through effortlessly.

Allow the gratin to rest for at least 10 minutes before serving. This helps the layers settle and makes cutting cleaner portions easier.

Serve warm as a luxurious side dish to roasted meats, lamb, or poultry. Its creamy richness pairs beautifully with crisp green vegetables or a light salad.