Trim any visible fat and tendons from the pork neck. Cut the meat into cubes roughly 3cm x 1.5cm. Peel the onions and cut into half rings. Peel the garlic cloves and finely chop them.
Prepare the marinade in a large bowl. Add the diced pork, half the onion rings, and chopped garlic. Mix well. Cover with foil and refrigerate overnight, at least 12 hours.
Two hours before grilling, remove the meat from the marinade and separate from the onions. Cut the 2 kiwis into very thin slices. Mix the kiwi slices with the meat.
After 2 hours, remove the meat from the kiwi slices. Do not leave the kiwi on the meat longer than 2 hours or it will become too soft and fall off the skewers. Thread the meat pieces onto skewers.
Heat the grill (wood, gas, or electric) to high temperature. Sear the skewers for about 1 minute on each side. Grill for about 4 minutes on each side until the pork reaches 63°C / 145°F internally.