Combine the buttermilk, 1/4 cup Essence, salt, sugar, and garlic in a large nonreactive bowl. Stir to blend. Immerse the chicken in the mixture, cover and refrigerate for at least 4 hours and for up to 24 hours.
Combine the flour, the remaining 1/4 cup Essence, and the cayenne in a large doubled brown paper bag or plastic freezer bag and shake to blend. Drop the chicken, a few pieces at a time, into the flour mixture and shake thoroughly to completely coat. Remove the chicken and shake off the excess flour. Repeat the coating process with the remaining chicken pieces. Place the coated chicken on a large wire rack set over a sheet pan and let rest until ready to fry, at least 20 minutes.
Heat 4 inches of oil to 300 degrees F over medium-high heat in a medium Dutch oven or heavy pot. Fry the chicken in batches, skin side down, until golden brown, about 10 minutes. Turn and fry until golden brown on the second side, 8 to 10 minutes longer. Remove the chicken and drain on paper towels. (Note: An even oil temperature is the key to success; a clip-on candy/deep-fry thermometer should be kept in the pot at all times. And the temperature should remain between 280 degrees F and 300 degrees F at all times.) Allow the chicken to rest at least 5 minutes before serving.