Peel, wash and chop carrots and celery, clean and wash leek and cut into rings. Wash meat, dab dry, rub with salt and pepper. Heat the oil in a roasting pan and fry the meat thoroughly all around.
Take the meat out and keep it warm. Roast the prepared vegetables in the frying fat, deglaze with wine and season with salt and pepper. Place meat on top, cover roaster. Braise in the preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: level 2) for about 2 hours.
Gradually add white wine and beef stock. Peel and wash the potatoes and cut into large cubes. Cook in boiling salted water for 10-15 minutes, drain and let it steam. In the meantime, clean and wash the chard and cut it into large pieces.
Blanch chard in boiling water for 1-2 minutes, remove. Peel onion and garlic and cut into fine cubes. Heat 1 tablespoon of oil in a large frying pan, sauté onion and garlic, add chard and potatoes and steam for 3-4 minutes while turning.
Season to taste with salt, pepper and nutmeg, keep warm. Halve the olives. Lift the roast out of the roaster, keep warm as well. Pour roast through a sieve into a pot, pass vegetables through the sieve, bring to the boil.
If necessary, stir the starch with 4-5 tablespoons of water until smooth and thicken the sauce. Simmer for 1-2 minutes, then add olives. Season to taste with salt, pepper and lemon juice. Cut the roast into slices.
Serve with sauce and potato-mangold vegetables.