Preparation

• Position a rack in the lower third of the oven, and heat the oven to 450°F.
• Press down on the chicken breasts with the heels of your hands to flatten a little; it’s OK if the wishbone cracks. If necessary, turn the legs so that the meatier side is on the same plane as the breast.
• Pat the chicken dry inside and out with paper towels. Sprinkle both sides of the chicken with 1-1/2 tsp. salt. Put the chicken breast side up on a rack over a rimmed baking sheet. Tuck the wings behind the back, and let stand at room temperature for 20 minutes.
• Meanwhile, put the peppercorns, coriander seeds, and mustard seeds in a spice grinder, and process until coarsely crushed. (Alternatively, use a mortar and pestle.) Transfer to a small bowl. Mix in the sugar, paprika, and garlic. Brush 1 Tbs. of the oil on the skin side of the chicken. Rub the spice mixture evenly over the chicken, pressing it into the skin. Put the remaining 2 Tbs. of oil in a large ovenproof skillet, preferably cast iron, and heat over medium heat until shimmering. Put the chicken in the skillet breast side down, and press down on it with a heavy-bottomed pan. Cook until the skin starts to sear and the spices are light golden, about 2 minutes. Flip the chicken breast side up, and transfer the skillet to the oven. Roast until an instant-read thermometer registers 160°F, 30 to 35 minutes.
• Remove from the oven, tent lightly with foil, and let rest for 20 minutes before carving and serving.