Peel the onions. Place the roast in a large pot with enough water to cover it. Add onions and spices (no salt!), bring to the boil and simmer covered for about 1 1/2 hours.
For the dough baking mix and 340 ml lukewarm water knead with the dough hooks of the hand mixer for 5 minutes to a smooth dough. Cover and let rise for about 30 minutes.
Lift out the meat, let it cool down briefly. Line a tray with baking paper. Knead the dough again. Roll out to a little flour about 1/2 cm thick and at least twice as big as the roast.
Dab meat dry, place on the pastry plate and spread with approx. 2 tbsp. mustard. Brush the edges of the dough all around with a little water.
Wrap the ham in the bread dough and press the edges well together. Place on the tray. Cover and leave to rise again for about 30 minutes. Preheat the oven (electric cooker: 200°C/circulating air: 175°C/gas: level 3).
Bake in a hot oven for about 1 hour. Wash herbs, shake dry. Puree with mayonnaise. Stir in yoghurt briefly. Season to taste with salt and pepper. Cut the roast open and serve with the herb sauce.