Directions: *Be careful with the open flame*
In a heavy skillet, melt butter over medium-high heat. Add brown sugar and stir together. Add cream and continue cooking, then stir in bananas and chopped walnuts. Mixture should be bubbly. (The steps so far should take less than 2 minutes; this is quick!)
Pour in rum and stir to combine. Carefully tip the skillet slightly toward the open flame of the burner to ignite the alcohol in the pan, then let the mixture flame for 30 seconds or so (it should go out on its own.) You can shake the pan a bit to get it to calm down. Remove from heat and stir in cinnamon.
Serve sauce immediately over vanilla ice cream or French toast. (Sauce does keep in the fridge, though. Delicious!)
* Note: You can omit the flame step altogether if you prefer. Just let the sauce cook for a minute or two–still utterly delicious!