One cup of coleslaw mix plus 1 tablespoon of sriracha can be substituted for the kimchi.
Combine kimchi, mayonnaise, and ¼ teaspoon pepper in bowl; set aside. In second bowl, whisk ketchup, soy sauce, oil, sugar, and garlic until smooth.
Cook beef and remaining ½ teaspoon pepper in 12-inch nonstick skillet over medium heat until beef is no longer pink and begins to brown, 8 to 10 minutes. Stir in ketchup mixture and cook until sauce thickens slightly, about 1 minute.
Divide beef mixture and kimchi mixture among bun bottoms. Cover with bun tops and serve.
