Heat broth to simmer. Add bay leaves, sauerkraut, and sauerkraut juice. Cook 30 minutes. Remove sauerkraut and set aside. Return liquid to a boil and add milk. In a small saucepan, melt butter. Add flour and cook about 2 minutes, whisking frequently to create a roux. Gradually add roux to pot to thicken soup, stirring with a wooden spoon. Soup should be thick and creamy. Return reserved sauerkraut to pot. Add corned beef and pepper. Stir in sour cream. Remove bay leaves. Makes 10 large servings. Top with cheese.