Prep all ingredients and set them on the counter next to the stove where you will prepare the bananas foster. Also have a longer lighter withing reach, for the flambé. Tie hair back, and lift any loose sleeve up.
Slice each banana once in half vertically, and once in half horizontally.
Caramel Sauce: Add butter to a cast iron skillet over medium heat. Once melted, stir in brown sugar and cinnamon. Cook over medium high-heat, stirring constantly, just a few minutes until bubbly and slightly thickened to syrup consistency. Stir in vanilla.
Add banana slices and cook for 1-2 minutes.
Flambé*: Tilt pan down slightly away from you and add the rum. Use a long lighter to immediately and carefully ignite a flame, to flambé the bananas foster. When the fire is going, carefully lift pan flat, a few inches above the stove burner and shake/swirl it gently back and forth, until the flames subside.
Serve: Add one or two scoops of vanilla ice cream to the center of a bowl. Add one banana slice to each side to cradle the ice cream. Spoon caramel sauce on top. Top with chopped walnuts, if desired.
