Heat oven to 350°F. Line broiler pan with foil. Spray rack of broiler pan with cooking spray. Arrange chicken on center of rack in broiler pan; sprinkle both sides with salt.
In large bowl, mix mayonnaise, mustard, oil, pepper and garlic; brush about 3 tablespoons mixture on chicken. Add potatoes to remaining mayonnaise mixture; toss. Arrange potatoes around chicken.
Bake uncovered 45 to 55 minutes, turning potatoes halfway through cooking, until potatoes are tender and juice of chicken is clear when center of thickest part is cut (170°F). Sprinkle with chives.