Whisk the mustard, honey, lemon juice, garlic, paprika, salt, pepper, and red pepper flakes in a bowl. Reserve ¼ cup of the sauce for later.
Place the chicken breasts in a zip-top bag and pour the remaining honey mustard sauce on top of the chicken. Massage to coat and allow the chicken to marinate for at least an hour.
Preheat your grill to 400°F. Cook the chicken breasts on the hot grill for 6 minutes on each side, or until the internal temperature reaches 160°F. Remove the chicken tent with foil and allow it to rest for 5 minutes. Drizzle with the reserved marinade before serving and sprinkle with parsley.
: Preheat your oven to 400°F. Place the chicken on a lightly greased baking sheet and cook for 25 minutes, or until the internal chicken temperature reaches 160°F. Drizzle with remaining marinade before serving and sprinkle with parsley.
