Wash the potatoes and cook for about 20 minutes. Clean the Brussels sprouts, beer.
For the stars, drain, quench, peel and hot press the potatoes. Knead with 2 egg yolks, 1 1⁄2 tsp. salt, nutmeg and 100 g potato flour. Roll out to a rectangle (approx. 20 x 25 cm) on some potato flour. Cut out stars of different sizes. Place on a baking tray lined with baking paper. Cover with cling film and put aside.
For the medallions, wash the fillets and dab them dry. Score the skin crosswise. Season flesh side with salt and pepper. Place 2 fillets with the meat side on top of each other. Cut off the ends. Cut the "double fillets" (with the skin side facing outwards into pieces about 5 cm wide) into 2 medallions each.
For the vegetables, roughly chop the nuts and roast them in a large pan with a lid. Remove. Heat 2 tablespoons of oil in the pan. Sauté the Brussels sprouts in it. Season with salt and pepper. Pour on approx. 1⁄4 l water. Bring to the boil, cover and cook for about 15 minutes. Drain and keep warm.
For the medallions, heat 1 tablespoon of oil in a frying pan. Sauté the meat first on the skin, then on the cut surfaces. Fry the cut ends with the meat. Fry the meat on a second tray in a hot oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for approx. 10 minutes.
For the sauce, peel and finely dice the shallots. Drain some duck fat. Brown the shallots in the remaining duck fat. Stir in the stock, cognac and jam, bring to the boil and simmer at low heat for about 5 minutes. Pour the sauce through a fine sieve into a small pot. Stir starch and 2 tablespoons of water until smooth. Bring the stock to the boil, stir in the starch and simmer for about 1 minute. Season to taste with salt and pepper.
Take the meat out of the oven, wrap it in aluminium foil and let it rest for about 10 minutes. Turn up the oven (electric cooker: 225 °C/circulating air: 200 °C/gas: see manufacturer). Wash the thyme and remove the leaves. Grate cheese. Whisk 1 egg yolk and 1 tbsp. water. Brush potato stars with egg yolk. Sprinkle with cheese and thyme. Bake in the oven for about 10 minutes. Mix sprouts with nuts. Arrange everything.