Place the chicken breasts in a shallow bowl.

In a separate bowl, mix together the crushed garlic, salt, brown sugar, grainy mustard, cider vinegar, lime juice, and lemon juice.

Blend well.

Whisk in the olive oil until the marinade is fully combined.

Season with black pepper to taste.

Pour the marinade over the chicken breasts, ensuring they are fully coated.

Cover the bowl and refrigerate overnight, allowing the chicken to marinate.

After marinating, remove the chicken from the refrigerator 1 hour before cooking to allow it to come to room temperature.

Preheat your grill to medium-high heat.

Grill the chicken breasts for approximately 4 minutes per side or until they are cooked through and no longer pink in the center.

Serve the grilled chicken hot, alongside your favorite sides or salads.