Marinate chicken in buttermilk and hot sauce for 15 minutes while you prep the slaw and sauce.
Toss cabbage, red onion, and pickles with vinegar, honey, and salt. Chill to let flavors meld.
Whisk mayonnaise, Dijon, hot sauce, pickle brine, and pepper until smooth. Set aside.
Drain chicken and pat dry. Season with salt, paprika, garlic powder, onion powder, and black pepper.
Heat oil in a large skillet over medium-high. Sear chicken 3–4 minutes per side until browned.
Lower heat, cover, and cook 3–5 minutes more, until chicken reaches 165°F. Rest 5 minutes, then slice.
Stir melted butter with garlic powder. Brush bun cut sides and toast in skillet or under broiler until golden.
Spread sauce on buns, add warm chicken and a mound of slaw, then cap and serve immediately.