Place all ingredients for the sauce in the blender and blend until completely smooth. Place the blended sauce in a large shallow pan over medium heat and let reduce for 10-12 minutes, whisking occasionally.
While the sauce reduces, make kabobs: on metal skewers, add a couple pieces of chicken close together, then a cube of pineapple, and repeat until the skewer is full. Repeat on 6-7 skewers. On each kabob, sprinkle with ginger, salt, garlic powder and a bit of black pepper, on all sides of kabobs.
Heat up grill or grill pan and grease. Place kabobs on hot grill and cook on each side for 2-3 minutes, for a total of 8-12 minutes, until no pink remains in chicken. During the last couple minutes of cooking, brush the kabobs with some of the sauce to coat. Repeat with all kabobs.
Garnish with green onions and toasted cashews and place the rest of the remaining sauce in a bowl for extra dipping!