Dab meat dry. Mix paprika powder, cayenne pepper and 1 teaspoon salt. Rub the meat with the spice mixture and cover and leave to cool overnight. Peel and finely chop the garlic. Wash thyme, shake dry, remove leaves from 4 stems and chop finely.
Heat the oil in a small pot. Sauté the garlic and thyme briefly while turning. Add tomato paste and sauté briefly. Add vinegar, stock and sauce. Simmer for about 5 minutes, stirring occasionally.
Place the meat in a roasting pan and brush with about 1/3 of the sauce. Cover and braise in a preheated oven (electric cooker: 125 °C/ circulating air: 100 °C/ gas: see manufacturer) for approx. 7 hours, occasionally sprinkle with the resulting broth.
After about 6 hours, add the remaining thyme, except for a few stems for garnishing. Drain pearl onions and add to the meat. Finish cooking the meat in an open roaster.
In the meantime peel, wash and halve the potatoes. Cook the potatoes in boiling salted water for about 20 minutes. Clean and peel the carrots, leaving some green on the carrots. Cook in boiling salted water for about 3 minutes.
Pour off, let it drip off, take the meat out of the roaster and wrap it in foil. Remove thyme stalks from the sauce. Place carrots in the broth. Heat milk and butter in a saucepan. Season to taste with salt and nutmeg.
Drain the potatoes and press them through a press into the hot milk mixture. Stir briefly.
Take the meat out of the foil and tear it up with the help of 2 forks. Drain the broth, add to the meat with the remaining marinade and mix. Arrange mashed potatoes, about half of the meat, sauce, pearl onions and carrots on plates.
Garnish with thyme. Use the rest of the meat for other purposes.