Preheat your grill to medium (350-400ºF).
Combine the butter and brown sugar in a small saucepan and cook over medium-low heat until the butter is completely melted and the sugar is dissolved.
With a sharp knife, cut each banana in half lengthwise, leaving the peel on the halves.
Brush the cut side of the banana halves with the sugar mixture and place the bananas cut side down on the grill.
Grill until golden brown and caramelized, about 2 minutes.
Turn the banana halves over, peel side down and brush each with more glaze.
Grill 2-3 minutes longer or until tender.
Remove the grilled bananas and place into a sundae dish or shallow bowl.
Top with two scoops of vanilla ice cream, drizzle with your favorite dessert sauce, and top with whipped cream and chopped nuts.
