Bring a large saucepan of salted water to the boil and add the meat.
Skim off the resulting foam from the surface.
Simmer half-covered for 3 hours, keeping the liquid just below boiling point.
Wash the carrots, celery, onions and leeks, cut the carrots and celery into sticks, the onions into wedges and the leeks into slices.
During the last 30 minutes of cooking, add the vegetables to the beef, making sure the meat is always covered with water.
Remove the meat from the pan.
Place on a plate and cut into slices.
Serve the drained vegetables with the meat. Garnish with parsley.
Meanwhile, peel and finely grate the horseradish.
Whip the cream until stiff, and place in a bowl with the horseradish.
Stir and season with salt.
Peel, wash and dice the potatoes.
Place in a saucepan.
Cover with meat broth and simmer for 20 minutes. Serve with the meat.