Preheat grill to medium-high heat.

Combine mint, lime juice, rum, honey, ¼ teaspoon salt, and pepper in a small food processor. Pulse for 10 to 15 seconds. Or whisk mixture well in a small bowl. Reserve a couple of tablespoons for serving; pour the rest in a medium bowl. Add chicken pieces and toss to coat. Let stand for 20 minutes.

Cut the ends off the onions; peel off the thin, papery outer skin. Cut onions in half along the equator. Cut each half in half again; you’ll have 16 quarters.

Thread onions and chicken onto separate skewers. Grill the chicken for about 8 minutes. Turn and brush with the remaining marinade and grill about 8 minutes more, or until the internal temperature reaches 165 degrees F. Grill the onions, turning occasionally and until slightly charred, about 4 minutes per side.

Sprinkle the chicken and onions with the remaining 1/4 teaspoon salt and drizzle with the reserved 2 tablespoons marinade. Serve with a whole grain and a salad.