Grilled Chicken with Rustic Mustard Cream

Ingredients     1 tablespoon plus 1 teaspoon whole-grain Dijon mustard, divided     1 tablespoon olive oil $     1 teaspoon chopped fresh rosemary     1/4 teaspoon salt     1/4 teaspoon black pepper $     4 (6-ounce) skinless, boneless chicken breast halves $     Cooking spray     3 tablespoons light mayonnaise $     1 tablespoon water     Rosemary sprigs (optional) Preparation     1. Prepare grill.     2. Combine 1 teaspoon mustard, oil, and next 3 ingredients in a small bowl; brush evenly over chicken. Place chicken on grill rack coated with cooking spray; grill 6 minutes on each side or until done.     3. While chicken grills, combine 1 tablespoon mustard, mayonnaise, and 1 tablespoon water in a bowl. Serve mustard cream with grilled chicken. Garnish with rosemary sprigs, if desired.