Finely grate the parmesan. Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Peel and wash the potatoes and slice or slice them very thinly. Layer the potatoes fan-shaped in a greased gratin dish.
Season individual layers with salt and sprinkle with parmesan. Pour 100 g cream over them. Bake in a hot oven for about 40 minutes.
Dab fillet steaks dry and tie with kitchen string. Dice gorgonzola. Wash parsley, shake dry and chop finely. Apple wash, quarter, core and cut into slices. Mix with lemon juice.
Heat 1 tablespoon of oil in a frying pan. Sauté the steaks in it for about 1 minute on each side. Then fry on each side for approx. 3 minutes at medium heat. Season with salt and pepper. Remove from the pan, wrap in aluminium foil and leave to rest for about 10 minutes.
Deglaze the roast with red wine, stir in plum puree, bring to the boil. Simmer for 6-8 minutes at low heat. Season with salt and pepper.
Meanwhile, bring 100 g cream and 5 tbsp water to the boil in a small pot. Melt the gorgonzola in it. Simmer on low heat for 3-4 minutes. Season with salt and pepper.
Heat 1 tbsp. butter in a frying pan, steam apple slices for approx. 2 minutes while turning, sprinkle with sugar and caramelise slightly.
If necessary, pass the red wine sauce through a fine sieve. Remove gratin from the oven. Arrange the fillet steaks with apple wedges, potato gratin and both sauces. Sprinkle with parsley.