- Place basil, chives, mayonnaise, yogurt, and olive oil in a blender or food processor. Squeeze in lemon juice. Purée until smooth and creamy; stir in salt and pepper to the herby dressing.
- Spread a layer of the herby dressing on each slice of bread. Divide avocado between 2 slices of bread; season with salt and pepper. Top each slide of bread with romaine, cucumber, Havarti (or Mozzarella), and close up the sandwiches. Enjoy!