Divide the graham crackers between two serving bowls, breaking them into pieces.
Toast the marshmallows:
Place the marshmallows on long sticks or skewers, and toast them over the fire until they are lightly browned on the outside (or a little charred if you like them that way) and becoming gooey in the centers.
Push the marshmallows off the skewers into the bowls with the crackers, two marshmallows per bowl.
Cook the bananas:
Peel the bananas and slice them into ½-inch thick slices. Keep the bananas close at hand as you prepare the sauce.
Place the skillet on the grate over the hot fire or coals and add in the butter. Melt the butter and then add the brown sugar.
Stir the sugar and butter until the mixture is smooth and bring it to a simmer in the skillet. Simmer and stir the sauce for about 3 minutes until it becomes thick and caramelized (longer if your fire is not as hot.)
Carefully add the rum, vanilla, and sliced bananas to the pan and gently stir everything together. Cook the bananas for about 2-3 minutes until they have softened a little.
Finish the dish:
Remove the skillet from the heat and pour the bananas and sauce over the marshmallows and grahams, splitting the mixture evenly between the two bowls. Serve the Bananas Fosters immediately!
Notes
To make a nonalcoholic version, simply omit the rum from this recipe.
If you're making this in your kitchen instead, you can toast the marshmallows over your stove burner. And cook up the bananas and rum in a skillet.