For the marinade, peel and chop 1 onion. Crumble the bay leaf. Crush the peppercorns slightly. Mix everything with wine. Wash the fillet, dab dry and put it in a freezer bag. Add marinade, close bag and chill overnight.
For the strudel dough in the package, let it rest for 10 minutes at room temperature. Wash parsley, shake dry, chop finely. Mix with sour cream and season with 1 tsp salt, 1/2 tsp pepper and 1 pinch of nutmeg.
Peel, wash and cut the potatoes into small cubes (approx. 1 x 1 cm). Mix with sour cream.
Preheat oven (electric cooker: 200°C/circulating air: 175°C/gas: level 3). Cover a baking tray with baking paper. Melt 75 g butter. Place 1 strudel sheet on a tea towel and brush with some butter.
Place the rest of the pastry sheets on top and brush each with butter. Spread the potatoes on the lower half of the dough, leaving a margin of about 2 cm at the sides. Whip the side edges over the filling. Roll up with the help of a cloth.
Place on the sheet with the seam facing down. Spread the strudel with the rest of the butter. Bake in the oven for about 30 minutes. Cover if necessary.
Remove the fillet from the marinade and dab dry. Heat 2 tablespoons of oil in a pan (with lid). Brown the fillet in it all around for about 10 minutes. Season with salt and pepper. Pour marinade through a sieve, bring to the boil, cover and braise for approx. 20 minutes.
Peel garlic and remaining onion and dice very finely. Crumble the bread finely. Wash and clean the beans and cut into short pieces (approx. 1 cm). Cover and cook in boiling salted water for 8-10 minutes.
Heat 2 tablespoons of butter. Roast the breadcrumbs in it for about 5 minutes. Fry the onion and garlic for 3 minutes. Season with salt and pepper. Drain the beans and mix with the breadcrumbs.
Remove the fillet. Boil down the stock at high heat for 3-5 minutes. Season to taste with salt and pepper. Cut strudel into thick slices, fillet into thin slices. Spread the fillet on plates fan-like and sprinkle with stock.
Arrange bean crunch and strudel on top.