Step 1

In a medium skillet over medium heat, toast cumin, coriander, and fennel seeds until fragrant, about 2 minutes. Transfer to a spice grinder or mortar and pestle and grind to a fine powder. In a food processor, purée onion, garlic, and ginger to a fine paste, 30 seconds.

Step 2

Heat oil in skillet over medium-high heat. Add onion mixture and cook until translucent, 4 to 5 minutes. Stir in spice mixture and turmeric. Let cool completely, then stir in yogurt and 1 1/4 teaspoons salt.

Step 3

Rub some of yogurt mixture all over chicken; then gently separate skin from breast and rub more under skin on each side. Place chicken in a resealable plastic bag and refrigerate at least 12 hours and up to 1 day. Bring to room temperature 1 hour before grilling.

Step 4

Prepare grill for direct- and indirect-heat cooking (push coals to one side of a charcoal grill, or turn off one side of a gas grill after preheating). Brush grates with oil. Place chicken over indirect heat, bone-side down, with legs closest to heat source. Cover grill and cook, maintaining a temperature of about 400°F, until a thermometer inserted into thickest part of breast (nearest but not touching bone) registers 150°F, 40 to 50 minutes.

Step 5

Transfer chicken to direct heat and cook, uncovered, flipping a few times, until charred in places and just cooked through, about 10 minutes more. Let stand 15 minutes before serving with chutneys, pickles, cucumbers, and mint.