Prepare the Chicken: Start by patting your chicken breasts dry with kitchen paper. Place each breast between two sheets of cling film and, using a rolling pin or meat mallet, gently pound them to an even thickness of about 1.5-2 cm. This ensures even cooking and a tender bite. You should hear a soft thudding sound as you pound, aiming for consistency.

The Brine: In a large mixing bowl, whisk together the buttermilk and pickle juice. Submerge the pounded chicken breasts in this mixture, ensuring they are completely covered. The brine should have a slightly tangy, milky smell. Cover the bowl and refrigerate for at least 2 hours, or ideally 4 hours. This brining step is crucial for tenderising the chicken and infusing it with flavour.

Prepare the Breading Station: While the chicken brines, prepare your dry ingredients. In a large, shallow dish, whisk together the plain flour, cornflour, salt, black pepper, smoked paprika, garlic powder, onion powder, and cayenne pepper (if using). The mixture should be a pale, uniform beige colour with a warm, spiced aroma.

Breading the Chicken: Remove one chicken breast from the buttermilk brine, letting any excess drip off. Do not pat it dry; the wet surface helps the breading adhere. Dredge the chicken liberally in the seasoned flour mixture, pressing firmly to ensure the coating sticks well. You want a thick, shaggy, and fully coated piece of chicken, which will feel slightly heavy with flour. Repeat with the remaining chicken breasts.

Heat the Oil: Pour the vegetable or groundnut oil into a large, heavy-bottomed frying pan or skillet until it's about 2-3 cm deep. Heat the oil over medium-high heat until it reaches a temperature of 175-180°C (350-360°F). You'll know it's ready when a small pinch of flour sizzles immediately upon contact, creating a gentle hissing sound.

Fry the Chicken: Carefully place 1-2 breaded chicken breasts into the hot oil, ensuring you don't overcrowd the pan. Fry for 4-6 minutes per side, or until the chicken is a deep golden brown and cooked through. Use a meat thermometer to check that the internal temperature reaches 74°C (165°F). The crust should be visibly crisp and the chicken should smell wonderfully savoury and fried. Once cooked, transfer the chicken to a wire rack set over a baking tray to drain excess oil and keep it crispy.

Assemble the Sandwiches: Lightly toast your brioche or soft burger buns. Spread a generous layer of mayonnaise on both halves of each bun. Place a crispy fried chicken breast on the bottom bun, top with a few dill pickle slices, and then add the top bun. The warmth of the chicken will slightly soften the pickles, releasing their tangy aroma. Serve immediately.