Pat chicken thighs dry with paper towels. Rub with olive oil. In a small bowl mix kosher salt, black pepper, smoked paprika and brown sugar, then evenly rub onto both sides of the thighs.

Smoke or grill

Preheat smoker or covered grill to 275°F (135°C). If using a grill, set up for indirect cooking and add soaked applewood chips to a smoker box or directly on coals. Place thighs skin-side up on the grates away from direct heat. Add a small pan of chicken stock under the thighs to keep moisture. Smoke until internal temperature reaches 175°F (79°C), about 60–75 minutes (time will vary by thickness).

Rest and chop

Transfer thighs to a cutting board and let rest 10 minutes. Remove skin if you prefer less fat. Using two forks or a large knife, coarsely chop the meat into bite-size pieces. Toss the warm chopped chicken with the butter so it melts through and any accumulated juices; taste and adjust seasoning with a pinch more salt or pepper if needed.

Crisp slaw

Make the dressing

In a medium bowl whisk together mayonnaise, apple cider vinegar, Dijon mustard, honey, celery seed (if using), salt and pepper until smooth. Taste and adjust for acidity and sweetness.

Toss the slaw

Add shredded green and red cabbage, carrot and scallion to the dressing. Toss thoroughly to coat. Chill the slaw in the refrigerator for at least 15 minutes to let flavors meld and to keep it crisp.

Build & finish

Toast buns

Split sandwich rolls or brioche buns. Spread softened butter on cut sides. Toast on a hot skillet or under a broiler until golden and just crisp, about 1–2 minutes per side. If desired, brush the toasted bun interiors with a quick mixture of sherry or apple vinegar and lemon juice (mix the 1 tsp vinegar with the 1/2 tsp lemon) to add brightness.

Assemble sandwiches

Pile a generous portion (about 4–5 oz) of the warm smoked chopped chicken onto the bottom bun. Spoon 1/2 to 3/4 cup of the crisp slaw on top of the chicken. Drizzle with hot sauce if using and sprinkle with chopped parsley. Cap with the top bun and press gently.

Serve

Serve immediately while chicken is warm and slaw is crisp. Leftover chicken and slaw can be refrigerated separately for up to 3 days.