Peel and wash the potatoes and apples and cut them into thin slices or slices. Skin the sausage, also cut into thin slices
Wash the thyme. Peel the garlic. Chop both, mix with milk and cream. Season with salt and pepper and layer the prepared ingredients in a greased casserole dish. Pour cream over it
Bake in a hot oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for 45-50 minutes. Grate cheese. After approx. 25 minutes sprinkle over the gratin and bake until done