Trim each chicken breast to even thickness; slice horizontally if breasts are thick to make two thinner cutlets (aim for ~1/2" thickness). Place the chicken in a shallow container and pour buttermilk mixed with hot sauce over it. Cover and refrigerate 1 hour (or up to 4 hours) to tenderize and flavor.

Prepare dredging stations

In a shallow bowl combine flour, cornstarch, paprika, smoked paprika, garlic powder, onion powder, 1 tsp salt, black pepper and cayenne; whisk to blend. In a second shallow bowl whisk eggs with milk.

Dredge the chicken

Remove chicken from buttermilk (allow excess to drip off). First dredge each piece in the seasoned flour, then dip into the egg wash, then press again into the flour mixture for a double-coat. Shake off excess and place on a wire rack for 10 minutes to set the crust.

Frying & Finish

Heat oil

Pour vegetable oil into a deep skillet or Dutch oven to a depth of about 1 inch. Heat over medium-high until oil reaches 350°F (175°C) or a small piece of bread sizzles and browns in ~45 seconds.

Fry the chicken

Working in batches if needed, carefully lower the breaded chicken into the hot oil. Fry 3–4 minutes per side until golden brown and internal temperature reaches 165°F (74°C). Maintain oil temperature between 325–350°F by adjusting heat. Remove to a wire rack set over a sheet pan to drain; rest 5 minutes.

Toast buns

While the chicken rests, heat a skillet over medium heat. Spread butter on cut sides of potato buns and toast, butter-side down, until golden, about 1–2 minutes.

Pimento Spread

In a small bowl, combine chopped pimentos, softened cream cheese, mayonnaise, shredded cheddar, lemon juice, 1/4 tsp salt and 1/8 tsp black pepper. Mix until smooth and spreadable. Taste and adjust seasoning. Refrigerate until ready to assemble.

Chipotle BBQ Aioli

Whisk together mayonnaise, minced chipotle, BBQ sauce, lime juice, honey and 1/8 tsp salt in a small bowl until smooth. Refrigerate until assembly; stir before using.

Toppings & Assembly

Assemble each sandwich: spread about 1 tbsp pimento spread on the bottom bun. Place a lettuce leaf, then 2 tomato slices. Put the fried chicken piece on top of the tomato. Spoon about 1½ tbsp chipotle BBQ aioli over the chicken, add 3 pickle slices and a small handful (about 2 tbsp) of fried onions. Cap with the top bun. Serve immediately.