In a large bowl, combine the shredded chicken, mashed avocado, Greek yogurt, Dijon mustard, and lime juice. Mix until well integrated and creamy.
Add the finely chopped red onion, cherry tomatoes, and cilantro to the chicken mixture. Stir gently to combine all the ingredients without mashing the tomatoes.
Season with salt and pepper to taste. Adjust the lime juice and mustard if needed for a zingy flavor.
On a serving plate, arrange the mixed salad greens.
Top the greens with a generous scoop of the creamy avocado chicken salad.
Optionally, drizzle a bit more lime juice over the top and garnish with extra cilantro leaves for added freshness.