Combine the fenugreek, garam masala, sugar, garlic, cardamom, peppercorns, salt, yogurt, and tomato paste in a large bowl and mix well; set aside 1/4 cup of the marinade for basting. Add the chicken thighs and drums and coat well. Cover the bowl and let marinate in the fridge for 45 minutes to 4 hours.
When ready to cook, preheat a grill to medium-high. Remove the chicken pieces from the marinade and place on the hot grill. Basting regularly with the reserved marinade, cook until the chicken is done and juices run clear, about 35 to 40 minutes.