Heat the oven to 180C/fan 160C/gas 4. Butter a large baking dish, and add the potato slices in layers into the dish seasoning each layer generously. Bring the cream, milk, garlic and thyme to just before a simmer, and pour over the potatoes, removing the garlic cloves. Sit on a baking sheet (to prevent any spills) and transfer to the oven. Bake for 50 minutes until the potatoes are soft when you push a skewer or a knife into the centre, and sauce bubbling. Scatter over the comté and cook for another 10 minutes until golden. Serve with roast dinners or duck breast.