Iceberg Lettuce; Head Of In a small mixing bowl, combine vinegar, onion juice, sugar, mustard, and salt. Stir vigorously by hand or with electric mixer set on low. Whisking constantly, pour in oil in a slow thin stream, and continue to beat until dressing is smooth and thick. Stir in poppy seeds. Cut lettuce into 6 wedges and lay each on a chilled salad plate. Ladle on 2 or 3 T of the dressing or to taste.