In a large mixing bowl, combine the diced avocado and hard-boiled eggs.
Add the crumbled bacon to the bowl.
In a separate small bowl, whisk together the Greek yogurt (or heavy cream), mayonnaise (if using), and fresh lemon juice until well combined
Pour the yogurt mixture over the avocado, eggs, and bacon in the large mixing bowl.
Add the chopped fresh cilantro to the mixture.
Gently fold all the ingredients together until well combined.
Season with salt and pepper to taste.
Serve the creamy avocado egg salad immediately on toasted bread, as a sandwich filling, or as a topping for salads.