Preheat the oven to 160°C (320°F). Peel and thinly slice the potatoes (about 3mm thick). Rub the inside of a baking dish with a cut garlic clove, then butter the dish. Layer the sliced potatoes in the dish, seasoning each layer with salt, pepper, and a bit of grated cheese. In a saucepan, gently heat the double cream with the remaining garlic clove (crushed) until just simmering. Remove the garlic clove and pour the hot cream over the potatoes. Sprinkle the top with the rest of the cheese. Cover with foil and bake for 45 minutes, then uncover and bake for a further 25-30 minutes until golden and bubbling.