In a medium mixing bowl, combine the coleslaw mix, vinegar, mayonnaise, sesame oil, sugar, 1 teaspoon salt, and ½ teaspoon pepper. Mix well, cover, and refrigerate until serving time.
In a large skillet over medium-high heat, heat the olive oil. Add the onion and cook, stirring occasionally, until translucent and soft, about 5 minutes. Add the beef and pork and cook, breaking it up with a spatula, until no longer pink, about 5 minutes. Drain off the excess fat and add the Asian BBQ sauce. Cook, stirring, for 1 minute. Add the beef broth and lower the heat. Cook, uncovered, stirring occasionally, until the sauce reduces, about 10 minutes.
In a small bowl, combine the cilantro, green onions, and sesame seeds.
Serve the meat on the buns, topped with coleslaw, the cilantro mixture, and pickled jalapeños, if desired.