– Chop onions, set aside. Mix BBQ sauce, ketchup, beef stock concentrate, ancho chili powder, salt, pepper, cornstarch, and 2 tablespoon water. Set aside.
– On medium, heat oil in a cast iron or non-stick skillet. Sauté onions until softened or slightly caramelized, about 5 minutes.– Add beef to pan, breaking up with a spoon or spatula. Sprinkle with salt and pepper and cook until browned and almost cooked through.
– Add sauce to beef mixture. Stir to combine. Simmer on low heat until beef is cooked through and sauce is slightly thickened, about 3-4 minutes.– Spoon ¼ meat mixture onto each of 4 buns. Serve with pickles.