Wash legs of lamb and pat dry. Wash herbs and pat dry. Pluck the leaves from the stalks, except for a little to garnish, and chop finely. Brush the legs of lamb with mustard on the inside. Fill with half of the herbs. Rub with salt and pepper.
Tie the meat together with kitchen string. Heat the fat in a roaster. Brown the meat all around. Peel, wash and cut the potatoes into pieces. Peel and halve shallots. Cut garlic into slices. Clean, wash and chop spring onions. Take the leg out of the roaster. Fry the potatoes, shallots and garlic in the frying fat. Add the legs again. Add spring onions, remaining herbs and olive oil to the roaster and braise in the preheated oven (electric range: 175 °C/ gas: level 2) for 35-45 minutes. Pour the roasting mixture over the meat several times in between.
Clean, wash and chop spring onions. Take the leg out of the roaster. Fry the potatoes, shallots and garlic in the frying fat. Add the legs again. Add spring onions, remaining herbs and olive oil to the roaster and braise in the preheated oven (electric range: 175 °C/ gas: level 2) for 35-45 minutes. Pour the roasting mixture over the meat several times in between. Wash, clean and chop the tomatoes. Add to the lamb shortly before the end of the cooking time