Preheat grill to high heat.
Meanwhile, peel pineapple and cut lengthwise into eight wedges; cut off the core. Place spears on a baking sheet and pour about two-thirds of the melted caramel butter over top; reserve the rest for basting. Turn to coat the spears all over in butter.
Grill pineapple for 3-4 minutes per side, basting with reserved caramel butter, until edges are caramelized and dark grill marks have formed.
Serve over vanilla ice cream and garnish with fresh mint.