Pre-heat the oven to 400F/ 200C
Mix the sauce ingredients- mirin, sake, soy sauce, sesame oil, sugar, and grated ginger- till the brown sugar has dissolved.
Add the sauce ingredients to a Ziplock Bag large enough to hold the chicken. Add the 1 inch chicken cubes to the sauce. Remove the air from the bag, seal tightly, and flip a few times so that the chicken is all covered with the sauce.
The chicken needs about 15-20 minutes to reach room temperature, and we'll let the meat marinade in the sauce for that time. (Don't cook cold chicken straight out of the fridge or it'll be tough.) Ideally, turn the bag every 5 minutes.
Whilst the chicken is marinating, soak or wet the skewers and prepare the cubed pineapples. (If using canned pineapple, you don't want them larger than the chicken pieces.)
After 15 minutes, start skewering the chicken and pineapple. Use about 2-3 pineapples per skewer. (There should be the same amoutn or more chicken than pineapple on each stick)
Place the sticks on the prepared baking sheet, ensuring there's a gap in between each. (We don't want them to steam!) Bake for 20-25 minutes, till the internal temperature at the thickest part of the meat is 165ºF (75ºC).
Whilst the chicken is cooking, transfer the marinade to a pot and boil till reduced to about half. (As the raw chicken was in it, it's crucial that you boil it well to kill all the germs.) After reducing, stir in ½ Tablespoon of honey.
To give the chicken a nice char, take it out of the oven 1-2 minutes early (i.e. after 18 minutes or so), lightly glaze with the thickened sauce then return to the oven for 1- 2 minutes. (Keep an eye on it to ensure it doesn't burn.)