For the brine:
- Remove skin from chicken and then cut into parts (breast, wing, thigh, and leg). Place in a baking dish and cover with brine, ensuring pieces are completely submerged. Cover dish and place in refrigerator for at least 3 to 6 hours.
- Remove chicken from brine and let dry on a paper towel-lined plate for 10 minutes.
- Heat chicken fat to 350 degrees in a large dutch oven.
- Pour buttermilk into a wide, shallow bowl and and cornmeal breading into another. Dunk chicken in buttermilk then toss in breading, ensuring each piece is evenly covered.
- Carefully lower each breaded breast into hot chicken fat. Fry for 2 to 3 minutes, then add legs, thighs, and wings. Fry until thickest part of each piece registers at least 165 degrees on a meat thermometer, 10 to 12 minutes. Carefully remove each piece and drain on a paper towel-lined plate. Sprinkle with salt to season.
Make a sachet of peppercorns and bay leaves in a bundle of cheesecloth. Combine water, salt, garlic, thyme, and sachet in a saucepan and bring to a boil, just long enough to dissolve the salt. Remove from heat and allow to cool completely. Strain before using.
For the cornmeal breading:
Combine all ingredients in a bowl, stirring well to combine.