Preheat oven to 190°C.

Thinly slice Potatoes and Onion.

In an oven-safe dish coated with Butter, layer Potatoes and Onions.

Sprinkle lightly with Salt and Black Pepper between layers.

Pour Milk over the layers until about two-thirds covered.

Top generously with Cheese.

Bake for 60 minutes, or until Potatoes are tender and the top is golden brown and bubbling.

Let rest for 10 minutes before serving.