Make the brine by dissolving the salt, sugar, and paprika in the buttermilk in a large container (I used a 13x9 Pyrex baking dish and it was filled to the rim after the chicken was added). Add the garlic and bay leaves, then submerge the chicken on the brine, cover, and refrigerate for 2-3 hours.
Remove chicken from brine, shake off excess brine, and place on a single layer on a wire rack set over a rimmed baking sheet. Refrigerate uncovered for 2 hours (In my opinion, you can skip this step, but if you have time go ahead with it).
Preheat the oven to 200 F, this is for keeping the chicken warm as you fry. Measure 2 inches of oil into a large Dutch oven and heat over medium-high heat to 375 F. You will need a thermometer, or you can use a deep fryer with built in thermometer if you have one. I have made this recipe successfully with both methods.
For the coating, place the flour into a shallow dish. In a separate medium bowl, whisk the egg, baking powder, and baking soda together, then whisk in the buttermilk (it will bubble and foam a bit). Dredge a piece of chicken in the flour, then coat in buttermilk mixture (allow excess to drip off), then coat in flour again and gently shake off the excess. Return chicken to wire rack. Repeat until all pieces are coated.
When the oil is ready, add as many chicken pieces to the pot as you can without crowding them. Place them in skin side down, cover the pot, and fry until deep golden brown, 7-11 minutes, adjusting the heat as necessary to maintain an oil temperature of about 325 F. After 4 minutes, check for even browning and rearrange if necessary. Turn pieces over and continue to cook until instant read thermometer registers 160-165 for breasts, or 170-175 for thighs or drumsticks, 6-8 minutes more.
Drain chicken briefly on paper towels, then transfer to a clean wire rack set over a rimmed baking sheet and keep warm in the oven.
Return oil to 375 F and repeat with remaining chicken pieces. Serve!