Heat oil in a deep fryer or large pan on the stove (a few inches deep) to 325°F.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, pepper, and garlic powder.
In another bowl, whisk together the buttermilk, egg, and hot sauce.
Dredge the chicken in the flour mixture, then dip into the egg mixture, and then back into the flour mixture, making sure to press down the flour to adhere well to the chicken.
Fry the chicken in the pan/deep fryer for 3-5 minutes on each side until golden brown. Remove and drain on a paper towel-lined plate. Repeat with all the chicken.
For the gravy, in a large pan, add 1/4" of oil from cooking and heat on medium-high. Stir in your flour until absorbed and cook for about 1 minute. Slowly add in your milk, whisking to blend, and heat until thickened. Stir in salt and pepper to taste.
Pour gravy over individual chicken pieces before serving.