Clean and preheat a grill to hot. Place the unpeeled bananas on the grill. Grill just until the skins begin to turn dark about 2 minutes, rotating as needed.
Remove the bananas from the grill. Slice the bananas lengthwise down the middle. Be sure not to cut completely through. Spread the bananas apart.
Fill the middle of each banana with a layer of chocolate chips, followed by the peanut butter chips.
Place the bananas back on the grill on indirect low heat and shut the lid. Grill just until the chips begin to softened. Spoon about 1 - 2 tablespoons of the condensed milk on top. Close the grill and continue to grill until the milk has warmed through.
Remove and serve with nuts, ice cream or whipped cream, if desired.
