Step 1

Rinse beef under cold water; pat dry with absorbent paper. Place beef, onion, carrot, celery, peppercorns, vinegar and sugar in a 4.5-litre (18-cup) slow cooker.

Step 2

Add enough of the water to barely cover beef. Cook, covered on low for 8 hours.

Step 3

Remove beef from cooker; discard liquid and vegetables. Cover beef to keep warm.

Step 4

Make horseradish sauce. Heat milk until hot. Melt butter in a medium saucepan, add flour; cook, stirring, 1 minute. Gradually add milk, stirring, until sauce boils and thickens. Stir in horseradish cream and parsley. Season with salt and pepper.

Step 5

Serve beef with sauce.