-chives for garnish -(optional) Thoroughly was leek leaves, which tend to collect sand. Trim off and discard root ends and all but about 3 cm of green tops. Peel off and discard 1 to 2 layers of tough outer leaves. Cut leeks crosswise into 1 cm pieces. In Dutch oven or large saucepan, melt margarine over medium heat. Add leeks and 3 Tablespoon. of stock; cook, stirring frequently, about 10 minutes, until leeks are tender but not browned. If liquid begins to evaporate, lower heat slightly and add more stock. Add remaining chicken stock, potatoes, broccoli and pepper. Lower heat, cover, and simmer about 11-14 minutes, until potatoes and broccoli are tender. Remove pot from heat and let cool slightly. In batches, puree mixture in a blender on low speed 10 seconds. Then raise speed to high and puree until completely smooth. Return puree to pot in which it was cooked. Add milk; stir to mix well. Simmer an additional 4 5 minutes. Refrigerate about 5 hours. Before serving stir in lemon juice and add salt, if desired. Garnish with chopped chives. Yield: 8 servings, each containing 163 calories, 6.7 grams protein; 2.8 grams fat; and 5 milligrams cholesterol.