Preparation Place basil, chives, mayonnaise, yogurt, and 2 Tbsp. oil in a blender. Finely grate in zest from a lemon half, then squeeze in its juice. Purée until smooth; season dressing with salt and pepper. Place cucumber in a small bowl; squeeze in juice from remaining lemon half. Drizzle with oil, season with salt and pepper, and toss to coat. Spread one side of each slice of bread with dressing. Divide avocado between 2 slices of bread; season with salt and pepper. Top with cucumber, mozzarella, and sprouts and close up sandwiches.
Preparation Place basil, chives, mayonnaise, yogurt, and 2 Tbsp. oil in a blender. Finely grate in zest from a lemon half, then squeeze in its juice. Purée until smooth; season dressing with salt and pepper. Place cucumber in a small bowl; squeeze in juice from remaining lemon half. Drizzle with oil, season with salt and pepper, and toss to coat. Spread one side of each slice of bread with dressing. Divide avocado between 2 slices of bread; season with salt and pepper. Top with cucumber, mozzarella, and sprouts and close up sandwiches.