Cut the beef into 1/8 inch (0.5 cm) strips and set aside. To make the marinade, combine 1/2 cup (125 ml) of oriental dressing, brown sugar, coriander, and ginger. In a large oven-safe dish (not aluminum) or a plastic bag, pour 1/4 cup (50 ml) of the marinade over the meat and turn to coat. Cover or seal the bag and refrigerate for up to 2 hours, turning occasionally. Refrigerate the remaining marinade. Meanwhile, in a small bowl, combine peanut butter, remaining oriental dressing, curry powder, and red pepper flakes. Remove the meat from the marinade and discard the marinade. Thread the strips onto skewers and grill, brushing frequently with the refrigerated marinade, for 2 minutes or until the meat is cooked to your taste. Serve with the peanut sauce.