Add onion, garlic, hot sauce, garlic salt, smoked paprika, and cajun seasoning to a food processor. Blend until a uniform puree/paste forms.
Add chicken to a large bowl and coat in the puree. Pour in the buttermilk, making sure that the chicken is fully submerged in the buttermilk. Cover with plastic wrap or a lid and allow chicken to soak in buttermilk brine for 2 hours (up to overnight) in the refrigerator.
Remove chicken from the buttermilk, removing as much of the marinade as possible. Then pat dry with paper towels – save the buttermilk mixture.
Add flour, cornstarch, baking powder, garlic salt, garlic powder, smoked paprika, onion powder, oregano, thyme, and Sazon to a large bowl. Whisk together.
Add eggs to the reserved buttermilk mixture and whisk together until combined.
Place chicken into the flour mixture, then dunk into the buttermilk marinade, then dip back into the flour mixture. Make sure to really coat the chicken in the flour coating, this is what gives the chicken its crispy crust. Place onto a wire rack and let the chicken rest at room temperature while the oil heats.
Heat oil over medium heat in a deep skillet or pot, oil should be about 4-5 inches deep in the pan. Heat to roughly 350-375 degrees Fahrenheit.
Fry 2-3 pieces of chicken at a time and let the chicken cook until crispy and golden brown, about 8-10 minutes. (Cooking time will vary with the thickness of the meat. To ensure chicken is thoroughly cooked, use a meat thermometer to ensure the internal temperature of the chicken is 165 degrees F.)
Melt butter in a skillet, then add ¼ cup of the frying oil. Add the spices, brown sugar, honey, and kosher salt. Cook for 2-3 minutes, then add in chicken broth and stir until fully incorporated. Remove from heat. Drizzle on top of the chicken.
Notes
Use an instant-read thermometer or candy thermometer (my preference) to monitor the oil temperature. Try to keep it between 350°F-375 degrees F. Too hot and the crust burns before the chicken cooks; too cool and it turns greasy.
If you have any remaining chicken thighs, make them into a nashville hot chicken sandwich!
Adjust the amount of cayenne pepper to your liking! I like a medium heat but if you prefer mild, add less. For super spicy, add more!
Use room temperature chicken! Letting the chicken come to room temperature (about 20–30 minutes out of the fridge) ensures it cooks evenly and crisps up beautifully. Plus, it helps prevent the outside from browning too quickly before the inside is done.
Don't overcrowd the pot when frying! This can cause the temperature of the oil to drop and the chicken will become soggy. It can also cause the chicken to cook unevenly. Depending on the size of the pot/skillet, cook 2-3 at a time and keep an eye on your oil thermometer to ensure the oil temperature isn't falling too much.
Let the chicken rest after breading! This allows the breading to fully adhere to the meat so that it doesn't fall off while frying.