Combine the pickle juice, milk, and Greek yogurt or buttermilk in a bowl until fully blended, then add the chicken pieces making sure they’re covered. Cover and chill for at least 30 minutes to let the flavors seep in and tenderize the meat.
In a small bowl, mix together salt, black pepper, paprika, garlic powder, onion powder, and cayenne pepper to create the seasoning blend.
Remove the chicken from the marinade and dry thoroughly with paper towels to help achieve a good sear. Drizzle with olive oil and evenly coat with the prepared seasoning, tossing gently.
Heat a grill pan or non-stick skillet over medium-high heat and lightly grease with cooking spray or olive oil. Arrange the chicken in a single layer without crowding and cook for about 3 to 4 minutes on each side until charred and cooked through (internal temperature 165°F/74°C).
Transfer the nuggets to a plate and allow them to rest for 2 to 3 minutes to keep them juicy before serving.
Optionally, brush the hot grilled nuggets lightly with melted butter right after cooking to add a rich, buttery finish reminiscent of the original Chick Fil A flavor.