Combine all ingredients for marinade in a bowl and blitz with an immersion blender until smooth. Add cubed chicken to gallon sized ziploc bag and pour marinade over. Let sit for at least 1 hour.
Preheat grill or grill pan to medium high. Add onion and sweet peppers to a bowl with oil, salt, and pepper. Toss to coat.
Start to build skewers, alternating sweet peppers, onions and chunks of chickens. Reserve marinade from chicken.
Pour marinade into a small saucepan over medium-low heat. Allow to simmer, stirring regularlly.
Once grill or grill pan is hot, place skewers on. Cook for 7 minutes then turn and spoon marinade sauce over top. Cook for 7 minutes more and then turn and spoon marinade saucue over. Cook another 7 minutes then remove from heat.
Serve with any additional marinade sauce over top.