Combine all the marinade ingredients together and mix well. Set aside 3 tbsp of marinade to brush on top after cooking. Add the chicken breasts, coat and leave to marinate for at least 20 minutes.
Toss the sliced plantain in the olive oil and season.
Pre heat the grill to 220ºC and the probe temperature to 75ºC.
Insert the probe into the largest part of the chicken breast and cook until done.
Add plantain to the grill and cook for 3-6 minutes.