- On a work surface, cut each chicken breast into two or three cutlets. Cover with plastic wrap and slightly flatten with a mallet or rolling pin. Set aside.
- In a glass dish or sealable plastic bag, combine all the ingredients. Add the chicken and thoroughly coat with the marinade. Cover the dish or seal the bag and refrigerate for 30 minutes.
- Thinly slice one cucumber. Cut the remaining cucumber in half lengthwise, remove the seeds and cut into cubes. Set aside.
- In a bowl, combine the yogurt, onion, lime juice and garlic. When ready to serve, add the cucumbers and cilantro. Season with salt and pepper.
- Preheat the grill, setting the burners to high. Oil the grate.
- Discard the marinade. Season the chicken with salt and pepper. Grill the chicken for about 2 minutes on each side, or until it is cooked through. Serve with cucumber salad and garnish with the peanuts.