Prepare Lemon-Poppy Seed Dressing: Whisk dressing ingredients together. Chill until ready to use. Can be prepared in advance and kept in fridge.
In a large bowl, combine chopped chicken, strawberries, pecans, celery, green onion, mandarin oranges, and Lemon-Poppy Seed Dressing. Cover and refrigerate until cold, approximately 4 hours.
When chicken mixture has finished chilling, remove from fridge and mix in the dried lavender, if desired.
Using a 3-4” square cookie cutter, cut 1 square from the center of each slice of bread.
Place 3-4 tablespoons chicken salad mixture on each bread square. Top with a second square of bread. Repeat with remaining bread and chicken salad.
Garnish sandwiches with strawberry roses or slices, if desired. (Learn how to make strawberry roses here).