Prepare the bananas foster mix: Melt the butter in a deep skillet over medium heat. Stir in the brown sugar, cinnamon and nutmeg until dissolved and syrupy. Carefully add the rum - the mixture will sizzle and bubble enthusiastically. Allow to cook until the bubbling calms, then add the heavy cream and salt, stirring well to create a smooth mixture. Add the banana slices and cook for 2 to 3 minutes until the slices are soft. Remove skillet from heat.

Fill a large bowl halfway with cold water and ice. Pour the mixture into a smaller bowl and nest that bowl in the ice water. Keep the mixture cooling over the ice water while you prepare the ice cream, replenishing the ice as it melts.

Prepare the ice cream: In a medium bowl, whisk the milk and granulated sugar until the sugar is dissolved. Stir in the heavy cream and vanilla. Process in your ice cream maker according to the manufacturer's directions.

During the last five minutes of processing, spoon out about 1/2 cup of the vanilla ice cream into a small bowl and set aside. Add about 3/4ths of the cooled bananas foster mix into the ice cream maker and allow to blend. Just before you turn off the machine, add the remaining mix and let it swirl briefly in the ice cream.

Spoon the bananas foster ice cream into your popsicle molds, leaving about 1 inch of head room, then top off each mold with some of the plain vanilla ice cream. Freeze according to the molds' directions (don't forget to insert the sticks*).

Depending on the size and quantities of your molds, you might have leftover ice cream. Tragic. If so, store in an air-tight container and enjoy sneaking spoonfuls at your whim.

*Some popsicle molds have issues with the sticks shifting out of place during freezing. To avoid this, allow the ice cream to freeze part way, then insert the sticks.