1. For the vinaigrette, place the strawberries , lemon juice and sugar in a food processor with the knife attachment and process until smooth.
2. Continue processing, gradually adding the vinegar and oil. Process until thickened, about two minutes. Stir poppy in seeds at the end.
3. In a large bowl, combine the lettuce, chicken, oranges, celery, and scallion. Stir together. Pour dressing over salad right before serving, and toss to coat. Top with salted peanuts or almonds. Serve immediately.