In a medium bowl, whisk together the whole grain mustard, Dijon mustard, honey, olive oil, lemon juice, garlic, paprika, dried thyme, salt, and pepper until well combined. The mixture should be smooth and fragrant, with a perfect blend of the sweet and tangy notes.
Reserve a ¼ cup of the marinade for brushing on the chicken later. This step is crucial, as it adds even more flavor during the cooking process.
Pour the remaining marinade into a gallon Ziploc bag. Add the chicken breasts to the bag and seal it tightly. Gently massage the bag to ensure the chicken is thoroughly coated in the marinade. This not only infuses the flavor but also helps tenderize the meat.
Lay the bag flat on a large plate or baking sheet to catch any leaks, and place it in the refrigerator. Let the chicken marinate for at least 30 minutes, or for best results, up to 8 hours. The longer it marinates, the more flavorful it becomes.
When you’re ready to cook, preheat your grill to medium-high heat and oil the grates to prevent sticking. This ensures that your chicken cooks evenly and doesn’t cling to the surface.
Remove the chicken from the bag and place it on a clean plate. Discard the bag with the used marinade to avoid contamination.
Place the chicken on the grill and cook, covered, for 5 to 7 minutes, depending on the thickness of your chicken. You want it to develop a nice grill mark and a slightly crispy exterior.
Flip the chicken over and brush it with the reserved ¼ cup of marinade. This adds an additional layer of flavor and keeps the chicken moist while cooking.
Cook for another 5 to 7 minutes, ensuring the internal temperature reaches 165°F. Use a meat thermometer to check the doneness, as this is crucial for juicy, safe-to-eat chicken.
Once cooked, remove the chicken from the grill and allow it to rest for 5 to 10 minutes before slicing or serving. Resting is important as it allows the juices to redistribute, making for a more succulent bite.