Peel the onions. Clean and wash the carrots and leek and cut into large pieces. Wash the marjoram. Dab the boiled fillet dry and season well with salt and pepper.
Now fry the meat in a large frying pan in hot oil all around. Remove and fry the onions, leek and carrots in the fat. Then add the boiled beef again, together with the marjoram and stock.
Bring everything to the boil and place in the preheated oven for 1 1/4 hours (electric cooker: 175°C/circulating air: 150°C/gas: level 2).
Peel and wash the potatoes, cover and cook in salted water for about 20 minutes. In the meantime I peel and wash the kohlrabi, wash and quarter the apples and cut both into slices. Drizzle with lemon juice.
Remove meat from the roaster and keep warm. Pour the stock through a sieve into a pot and skim off the fat. Pour vinegar, bring everything to the boil and simmer for 12-15 minutes. The sauce tastes good.
Fry the kohlrabi and apples in 2 tbsp. hot butter. Sprinkle with 1 tbsp. sugar and let it caramelise briefly. Add 1/4 l water and stock. Bring everything to the boil and simmer for about 10 minutes.
Drain the potatoes. Warm the milk and pour it over the potatoes. Then work with the potato masher, stirring in the remaining butter. Season the mashed potatoes with salt, horseradish and nutmeg.
Wash the parsley. Some leaves I put aside for garnishing. I cut the rest into strips and mix it into the vegetables. Cut the boiled beef across the fibre (so that the meat stays tender) and arrange it with vegetables and sauce.
Garnish with parsley. Serve with the horseradish puree.