Wash and peel greens and dice them. Peel and dice potatoes also. Boil up soup, add vegetables and place the meat. Simmer over low heat, covered except for a small gap about 20 minutes until done. Preheat oven to 60 °. Cut chives finely. Mix starch with cold water until smooth. Remove meat, wrap in aluminum foil and put into the oven. Boil up vegetable stock, stir in starch and simmer about 1 minute. Season fond with salt and pepper. Remove meat from oven and cut into 2 cm thick slices. Serve with stock and vegetables. Serve sprinkled with chives and horseradish.