How to Make It
In a large skillet, toast the coriander seeds over moderately high heat, shaking the pan, until fragrant, about 1 1/2 minutes. Transfer to a spice grinder and let cool completely. Grind to a powder.
Score the duck skin in a cross-hatch pattern; season with salt and pepper. Heat the skillet. Add the duck, skin side down, and cook over moderate heat until the skin is browned and crisp, 5 minutes. Turn the breasts skin side up and sprinkle with the ground coriander. Cook until medium-rare, 4 minutes longer. Transfer the duck to a carving board and let rest for 5 minutes. Thinly slice the duck crosswise and serve with Grandma's Crushed Potatoes.