Whisk 1 cup plain whole-milk yogurt in a bowl. Add 1 1/2 teaspoons crumbled dried mint and 2 tablespoons grated onion. Mash 1 garlic clove into a paste with 1/2 teaspoon kosher salt; add to the yogurt along with 1/2 teaspoon pepper, 1 teaspoon lemon juice and a pinch of cayenne pepper. Season 8 frenched lamb rib chops with salt and pepper; marinate in the yogurt sauce for 1 to 4 hours. Preheat a grill to medium-high on one side and place a drip pan under the cooler side. Lightly oil the grate. Grill the chops over direct heat until marked, 3 to 4 minutes per side. Move to the cooler side of the grill; cover and cook until the meat reaches 120 for medium-rare, 15 minutes. Let rest 10 minutes.