In a small bowl, mix all of the seasoning ingredients together until well combined. Set aside 2 teaspoons of the seasoning mix for the coating later.
In a large bowl, combine the chicken fillets, milk, Greek yogurt, and the remaining seasoning mix. Mix thoroughly to ensure the chicken is evenly coated. Cover and let it marinate in the refrigerator overnight.
The next day, whisk together the all-purpose flour, cornstarch, baking soda, and the reserved 2 teaspoons of seasoning mix in a large bowl. Transfer 1/2 cup of this flour mixture to the marinated chicken and stir until a thick batter forms around the fillets.
Working with one piece at a time, drop a chicken fillet into the dry flour mixture. Use both hands to toss the chicken in the flour about 10 times.This helps create those crispy, craggy bits that make fried chicken extra crispy. Repeat with the remaining fillets.
Heat a pot of oil until it reaches 180°C (350°F). If you have a kitchen thermometer, use it for accuracy. Otherwise, dip a wooden chopstick into the oil, if small bubbles quickly form around it, the oil is ready.
Fry the chicken in batches for about 3 minutes, or until golden brown, crispy, and cooked through. Avoid overcrowding the pot, as this will lower the oil temperature and affect the crispiness. Keep an eye on the cooking time, as the chicken will continue to cook slightly from residual heat after frying.
Transfer the fried chicken to a wire rack or paper towel-lined plate and let it rest for 2 to 3 minutes. Meanwhile, whisk together the mayonnaise, Greek yogurt, and chili sauce until smooth.
Serve the crispy chicken hot with the creamy dipping sauce on the side.
