Scatter the lettuce over a large serving platter.
Make nice neat rows over the lettuce with the cumbled bacon, diced eggs, tomatoes, chicken, avocado, onion, and blue cheese (the order is of no consequence; whatever strikes you). Season with salt and pepper. You can drizzle Creamy Pesto Dressing over the salad, or serve it on the side.
Mix together the mayonnaise, buttermilk, basil, Parmesan, garlic, salt, and pepper in a blender until everything is well combined. Transfer to a plastic container. Refrigerate for up to 2 days until ready to serve.