Corned Beef & Cabbage w/ Horseradish Sauce

1 Onion
4 Cloves, whole
4 lb Corned beef
2 Parsley sprigs
8 Peppercorns, whole
2 lb Cabbage
1 cup Sour cream
1 tbsp Prepared horseradish

Peel onion and stick with cloves. Put corned beef, onion parsley and peppercorns in a large pot and cover with water. Cover, bring to a simmer and cook gently until tender, 2-1/2 to 3 hours. Cut cabbage into wedges and core. Add to the pot, cover and simmer until tender, about 30 minutes. Combine sour cream with horseradish. Serve the meat and cabbage with some of the broth ladled over all and the horseradish on the side.