Place the chicken breast in a shallow dish and pour the buttermilk over it, ensuring it is fully coated. Let it marinate for at least 20 minutes.
In a small bowl, whisk together the whole wheat flour, panko breadcrumbs, smoked paprika, garlic powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, allowing excess to drip off, then dredge it thoroughly in the flour and panko mixture, pressing to adhere.
Lightly coat the chicken with avocado oil and place it in an air fryer at 375°F for 12-15 minutes, flipping halfway through, until the internal temperature reaches 165°F.
While the chicken cooks, whisk together the Greek yogurt and hot sauce in a small ramekin to create the spicy spread.
Toast the sprouted grain bun until lightly browned.
Assemble the sandwich by spreading the yogurt sauce on the bun, then layering the lettuce, tomato, pickles, and the crispy chicken.