Wash and peel the potatoes and cut into slices approx. 1 cm thick. Wash and quarter the pear, remove the core and cut the pulp into slices. Cut the celery into 1 cm thick rings.
Put everything in a baking dish, season and mix well. Spread the mountain cheese on top. Put the gratin in the oven at 200 ° C for 30 to 45 minutes.
If you want, you can also sprinkle sunflower seeds or nuts on top.