chicken breast halves, skinless and boneless (4 ounces each)
ready-made white horseradish
dark brown sugar, firmly packed
Preheat broiler, heat a charcoal grill until coals form white ash, or preheat a gas grill to medium.
To prepare sauce, in a small saucepan, combine ketchup, vinegar, horseradish, brown sugar, garlic, and thyme.
Bring to a boil over medium-low heat.
Cook, stirring frequently, until thickened, about 5 minutes.
Brush tops of chicken pieces lightly with sauce.
Place chicken, sauce-side down, on a foil-lined broiler pan or grill rack.
Brush other sides lightly with sauce.
Broil or grill 3 inches from heat, basting with remaining sauce and turning until no longer pink in center, about 5 to 7 minutes per side.
Let chicken stand for 5 minutes before serving.