In the bowl of a food processor, combine the yogurt, mint, lemon, ginger, garam masala, brown sugar and salt and pulse until blended. (Alternatively, stir everything in a bowl, then finely chop the mint and stir it in.) Add the chicken, stir to coat well, and refrigerate for a couple hours, or overnight.
Meanwhile, soak bamboo skewers in water for at least 10 minutes and preheat your grill to medium-high. Thread the chicken onto the skewers and cook for about 5 minutes, turning as needed, until the chicken is cooked through. Serve as is or with beet chutney.