Using a stick blender or food processor the garlic, chillies, pepper, sugar, soy sauce and fish sauce with around ½ cup water.
Separate the pork and beef in two bowls (or small bags) and divide the marinade between the two. Mix well, cover and refrigerate for 24 hours (4 hours minimum). 24 hours will give the best taste!
Before you create the skewers, soak the some 6-inch wooden skewers in water for 2-3 hours. This will stop them completely disintegrating on the grill.
Thread the meat onto the skewers then grill on a hot BBQ grill for about 3-4 minutes per side to char and cook through.
Serve with a Thai dipping sauce and crunchy salad.