Preheat the oven to Gas Mark 1, 140ºC (275ºF). Peel the potatoes and cut them into thin slices. Overlap one-third of the slices over the base of a buttered 2.¼ litre shallow ovenproof dish and sprinkle with half the chopped garlic, one-third of the grated cheese and some salt and pepper. Repeat the layers once more, then finish with a final layer of neatly overlapped potatoes.
Warm the milk and cream together in a pan with a little more seasoning to taste. Pour over the potatoes and sprinkle with the remaining cheese.
Bake for approximately 1½ hours until the potatoes are tender when pierced with the tip of a knife. Cover very loosely with a sheet of foil part-way through cooking after the top has become nicely golden.