Place the trimmed chicken thighs in a bowl or zip-top bag. Add the buttermilk and hot sauce (if using). Toss to coat, cover, and refrigerate for at least 1 hour or up to 6 hours to tenderize and flavor the chicken.

Prepare the Dredge

In a large shallow dish, whisk together the all-purpose flour, cornstarch, kosher salt, black pepper, paprika, garlic powder, onion powder, and cayenne. Mix until evenly distributed.

Heat Oil

Pour vegetable oil into a heavy-bottomed skillet or Dutch oven to a depth of about 1 to 1 1/2 inches (approximately 3 to 4 cups depending on pan). Heat over medium-high until the oil reaches 350°F (175°C). If you don't have a thermometer, test by dropping a pinch of flour into the oil— it should sizzle and float.

Dredge the Chicken

Remove chicken from the buttermilk, letting excess drip off. Working one piece at a time, press each thigh into the flour mixture, coating thoroughly and shaking off excess. For an extra-crispy crust, dip the coated piece back briefly into the remaining buttermilk, then re-coat in the flour mixture for a double dredge.

Fry

Carefully lower 2 pieces (do not overcrowd) into the hot oil. Fry, turning occasionally, until golden brown and cooked through, about 4–6 minutes per side depending on thickness (internal temperature should reach 165°F / 74°C). Adjust heat as needed to maintain 325–350°F and prevent burning. Transfer to a wire rack set over a baking sheet and rest for 5 minutes. Repeat with remaining pieces.

For the Dill Lemon Aioli

In a small bowl, combine the mayonnaise, fresh lemon juice, lemon zest, chopped dill, minced garlic, honey, kosher salt, and black pepper. Whisk until smooth. Taste and adjust seasoning—add more lemon for brightness, more honey for balance, or more dill for herbiness. Refrigerate until ready to assemble (can be made up to 24 hours ahead).

For the Sandwich Build

Lightly toast the buns until golden. Spread about 1 to 1 1/2 tablespoons of the dill lemon aioli on the bottom bun of each sandwich.

Place a lettuce leaf on the aioli, then one piece of the fried chicken. Top the chicken with 2 tomato slices and a few thin red onion rings. Season the tomato lightly with the reserved kosher salt and black pepper. Add pickle slices if using.

Spread a thin layer of aioli on the top bun and close the sandwich. Serve immediately while the chicken is hot and crispy.