Peel the carrots and cut them in half lengthwise. Wash and clean the celery. Cut carrots and celery into slices. Peel and halve onions and cut into strips. Wash thyme and dab dry.
Dab meat dry.
Heat the oil in a frying pan. Fry the meat for approx. 10 minutes, turning it well. After approx. 8 minutes add vegetables and fry. Add tomato paste, sweat briefly and deglaze with tomatoes and stock.
Add thyme and bay leaf, season with salt, pepper and sugar. Stew in a closed roaster for about 2 1/2 hours until soft.
Wash, peel and cut the potatoes into pieces. Cook in boiling salted water for about 20 minutes. For the Gremolata, wash parsley, shake dry. Pluck off leaves and chop finely. Peel garlic and also chop finely.
Mix parsley and garlic with lemon peel. Heat milk and butter in a pot. Drain the potatoes and let them evaporate briefly. Add milk mixture and crush everything coarsely. Season to taste with salt and nutmeg.
Season stew to taste, remove thyme twigs. Arrange stew with mashed potatoes. Sprinkle with gremolata.