In a small bowl combine tuna and cabbage; toss to mix. Stir in yogurt and salad dressing.
Using a 4- to 4-1/2-inch cookie cutter, cut fish or other shapes from bread slices. Save bread scraps for another use. Spread tuna mixture on half of the bread shapes. Top with remaining bread shapes. If desired, decorate sandwiches with capers, olives, and/or raisins. Wrap tightly in plastic wrap. Chill up to 24 hours. Pack in insulated containers with ice packs. Makes 2 servings.