Put the leeks, onions and broth in a pot. Bring to a boil. Reduce the heat; cover. Simmer for 25 minutes. Add the potatoes; return to a boil. Cover and simmer for 20 minutes, or until the potatoes are tender. Process in a blender until smooth. Stir in the pepper.
TO SERVE AFTER FREEZING: Thaw as recommended. Reheat slowly, covered. Serves 12-14.
Per 1 cup serving: 154 calories, 6 grams protein, 30.5 grams carbohydrates, 2.8 grams fiber, 1 gram fat (0 grams saturated), 510 milligrams sodium.