In a medium bowl, whisk together yogurt, lemon juice, Dijon, and garlic, then slowly pour in buttermilk, whisking constantly.
Whisk in parsley and season with salt and pepper.
Place in fridge until ready to use.
In a large skillet over medium-high heat, cook bacon until brown and crisp, about 8.
Drain on a paper towel-lined plate until cool, then crumble.
Place lettuce in a large bowl.
For a pretty presentation, arrange toppings into colorful stripes: avocados, tomatoes, corn, bacon, and chicken.
Drizzle with buttermilk dressing and serve.