Heat butter in a large skillet over medium heat. Add turkey, onion, fresh jalapeno and garlic; cook until turkey is no longer pink and vegetables are tender, 8-10 minutes, breaking up turkey into crumbles.
Stir in ketchup, jalapeno juice, pickled jalapenos, brown sugar, Worcestershire sauce and seasonings. Bring to a boil. Reduce heat; simmer, uncovered, 15-20 minutes to allow flavors to blend, stirring occasionally. Serve on buns.
