Simmer 1 cup ketchup, 1/2 cup cider vinegar, 3 tablespoons each molasses and brown sugar, 1 tablespoon each dried mustard and soy sauce, 2 teaspoons Worcestershire sauce, 1 cup water, and kosher salt and pepper to taste until thickened, about 30 minutes. Preheat a grill to medium-high on one side. Season 4 bone-in, skin-on chicken breast halves with salt and pepper. Grill over direct heat until golden and crisp on both sides, about 5 minutes. Transfer to a bowl and toss with 1 cup of the sauce. Place on the cooler side of the grill; cover and cook, basting once, until the meat is glazed and reaches 165, 25 to 30 minutes.
Photograph by Tina Rupp