Peel the beetroot. Boil up salted water with a dash of vinegar. Cook the beetroot for about 40 minutes. Peel and wash the potatoes and cook in boiling salted water for about 20 minutes. Wash the meat, dab dry and cut into strips.
Clean the mushrooms and cut them in half. Cut cucumbers into strips. Heat oil in a large pan. Season meat with salt and fry it for 2-3 minutes while turning it over high heat. Add mushrooms and fry for another 2-3 minutes.
Add the cucumbers, deglaze with wine and cream and continue cooking for about 5 minutes. Remove the beetroot and let it cool down briefly. Mix the starch with a little water until smooth, thicken the sauce with it until slightly creamy. Season sauce with salt and pepper.
Cut the top off the beetroot. Hollow out the beetroot with a ball cutter or a teaspoon and keep warm. Meanwhile drain and mash the potatoes, add milk. Season the puree with salt, pepper and nutmeg.
Stir some of the released flesh into the sauce. Fill the beetroot with the shredded meat, arrange on preheated plates with the remaining shredded meat and the mashed potatoes. Garnish with marjoram.