Whisk together the Marinade/Sauce ingredients in a medium-bowl. Then remove ⅓ cup into a freezer bag & whisk in 3 tbsp olive-oil. Add chicken and toss to evenly coat.
Marinate in the fridge 6-hours to overnight. Fridge remaining marinade/sauce individually (this will become base of Peanut-sauce).
When ready to cook, then soak wooden skewers in warm water for a half an hour (minimum).
Meanwhile, remove chicken from fridge, then thread chicken on skewers and gently dab excess marinade off with paper-towels.
Preheat oven to 350°F. Line 2 baking-sheets with foil and spray with non-stick cooking-spray. Evenly divide chicken between-sheets.
Bake for 15-20 minutes, or till chicken is cooked by being careful to not overcook or chicken won't be as tender.
Grease a grill and heat to high-heat. Once hot, add chicken, reduce heat to medium, cover and grill chicken for 3-4minutes each side, or till chicken is cooked through.
Heat 1 ½ tsp olive-oil in a large-skillet over medium-heat. Working in batches, then add skewers & cook for 2-3minutes each side till cooked through.
Add reserved-sauce into a small saucepan along with ¼ cup coconut-milk or 3 tbsp water. Bring to a boil then simmer for a minute.
Remove from heat then stir fry in ⅓ cup peanut-butter till thoroughly combined and then add extra peanut-butter if needed to get a thicker or water or coconut-milk 1 tbsp at a time to get a thinner sauce. Taste and add extra chili-sauce if needed for a spicy-sauce
Serve chicken warm with peanut-sauce for an appetizer or you can serve with veggies or rice to get a main-course.