Rinse the chicken, and cut the chicken breast halves in half horizontally to make 10 pieces in all. Pat the chicken pieces dry with paper towels. Combine the buttermilk, hot pepper sauce, and garlic in a large plastic zipper bag. Add the chicken pieces, and squeeze the air out of the bag, close it, and refrigerate overnight.
The next day, preheat oven to 325 degrees F (165 degrees C).
Heat the vegetable oil in a large, deep-sided skillet over medium heat until the oil shimmers but doesn't smoke. Whisk together the flour, brown sugar, salt, black pepper, sage, paprika, and garlic powder in a large bowl. Remove 2 or 3 pieces of chicken at a time from the buttermilk mixture, and press into the flour mixture until well coated. Shake off excess flour.
Fry 2 or 3 pieces of coated chicken at a time in the hot oil until the crust is golden brown, 3 to 5 minutes (chicken meat may still be pink inside). Drain on paper towels, and place into a 9x13-inch baking dish.