Heat the oven to 375°F. Lightly grease 8 cups of a standard muffin pan.
In a large bowl, combine the ground turkey, egg, breadcrumbs, diced onion, 2 tablespoons of the barbecue sauce, Worcestershire sauce, garlic powder, smoked paprika, salt, and black pepper. Mix gently until just combined.
Divide the mixture among the 8 prepared muffin cups. Press it in lightly, leaving the tops rounded rather than packed down.
Bake for 15 minutes. Remove the pan and brush the tops with the remaining barbecue sauce. Return the pan to the oven and bake for about 10 minutes more, until the muffins are cooked through and reach 165°F in the center.
While the muffins bake, whisk the mayonnaise, apple cider vinegar, and honey in a medium bowl. Add the cabbage and apple, then toss until evenly coated.
Let the muffins rest in the pan for 5 minutes. Serve warm with the apple slaw alongside or spooned on top.