With a meat mallet or a rolling pin, pound the chicken to an even thickness between ¼-inch and one inch. Place the chicken in a large, sealable container or bag.
Whisk together the buttermilk and hot sauce and pour over the chicken. Refrigerate for at least 2 hours or overnight. If the chicken is not fully submerged, occasionally move it around so that all sides get to soak in the marinade.
In a large shallow dish, whisk together the flour, garlic powder, smoked paprika, cayenne, pepper, salt, baking powder and corn starch.
When the chicken is ready, remove it from the marinade.
Drizzle 3 tablespoons of the buttermilk marinade into the flour mixture and toss to form small clumps. Discard the remaining buttermilk marinade. Dip the chicken into the flour mixture and coat all sides, pressing to help the flour adhere.
Place the chicken on a wire rack, set over a sheet pan. In a deep fryer or heavy bottomed saucepan, heat enough shortening to have at least 3-inches of oil when melted.
Add a piece of chicken and fry for approximately 4-6 minutes per side. This will vary depending on the thickness of the chicken. Cook until the chicken is golden brown and the center reaches 165°F.
Toss cooked chicken in the buffalo sauce or drizzle it over the chicken breasts. Serve on a brioche bun with lettuce, tomato and pickles.
