Preheat oven to 400 degrees F.

To make the mustard rub, combine olive oil and whole grain mustard in a small bowl; season with salt and pepper, to taste. Using your fingers or a brush, work the mustard rub onto both sides of the chicken.

In a large bowl, whisk together Dijon mustard, whole grain mustard, honey and chicken stock. Add more chicken stock as needed until desired consistency is reached; set aside.

Heat olive oil in a large oven-proof skillet over medium high heat. Add chicken, and sear both sides until golden brown, about 2-3 minutes per side. Add mustard mixture and sprinkle with rosemary.

Place into oven and roast until completely cooked through, reaching an internal temperature of 175 degrees F, about 25-30 minutes.