Preheat a grill or frying pan until hot.
Rub the 4 skinless, boneless chicken breasts with 1 tablespoon of olive oil, 1 tablespoon of garam masala, and a pinch of salt.
Cook the chicken for 6 minutes on each side or until slightly charred and cooked through.
Peel and slice the mango into slim wedges.
Halve the 1/2 cucumber lengthwise, then slice thickly at an angle.
Thinly slice the 1/2 small red onion.
Toss the salad ingredients (mango, cucumber, onion) together with 1/4 cup of coriander leaves, then pile onto plates.
Mix 4 tablespoons of sour cream with the juice and zest of the 1/2 lime, season with a pinch of salt, then dollop beside the salad.
Cut the cooked chicken in half or into thirds diagonally, arrange next to the salad, and serve with naan bread.