About 20 bamboo skewers, soaked in water for about 1 hour before cooking
For the marinade: Place the chicken in a reseable plastic bag. Whizz up the oil, cilantro, lime juice, coriander, garam masala, serrano peppers and ginger in a food processor until smooth. Season with salt and black pepper. Pour over the chicken cubes, massage into the meat, and marinate in the fridge for at least 2 hours and up to 8 hours.
For the chutney: Toss the peaches, ginger, honey, vinegar, chaat masala, if using, chile flakes, cilantro and lime juice and zest into a food processor or blender and blend until smooth. Season with salt and black pepper. Pour into a serving bowl, setting aside 1/4 cup for basting the chicken.
For grilling the chicken: Preheat the grill to medium-high heat. Thread 4 to 5 chicken cubes onto two skewers at a time, lightly wiping off excess marinade with a paper towel. The cubes should be lightly touching, not tightly packed.
Grill the skewers on one side until golden brown, 5 to 7 minutes. Flip and baste with the reserved chutney. Grill the other side until golden brown, 5 to 7 minutes, then flip and baste again. Grill to seal the chutney glaze, another 30 seconds per side, then remove from the heat. Sprinkle with salt and a little more chaat masala, then serve with big bowl of the chutney.