Tafelspitz (Viennese poached veal with horseradish and apple sauce)

Ingredients

• 4.4 lbs veal tri-tip
• 3 1/2 oz jarred horseradish
• 5 oz horseradish
• 4 apples
• 1 lb potatoes
• 4 carrots
• 14 oz celery roots
• 1 1/2 stalks leeks
• 1 onion
• 2 tbsp parsley
• 1 clove garlic
• 1 bay leaf
• 4 allspice berries
• 1 clove
• 10 1/2 water
• 1 tbsp sugar
• 1/2 cup apple juice
• 1/2 stick unsalted butter
• 1/2 cup flour
• 1/4 tsp ground nutmeg
• 1 cup heavy cream
• 1 tbsp mustard
• 2 tbsp chives
• salt
• pepper