Cut bananas in half lengthwise, then widthwise. Layer on the bottom of a 1.5 qt ovenproof casserole dish.
In a small bowl, mix brown sugar, orange juice, butter, rum and cinnamon. Whisk thoroughly. Spoon over the bananas, and use a pastry brush to ensure the bananas are thoroughly coated. Cover with an ovenproof lid.
Place the Oven Rack in the Slow Cook/Proof level and place the covered casserole on the rack.
Select the SLOW COOK program and adjust the time to 2 hours, then press START.
When the program is complete, divide the bananas into individual serving dishes, toss toasted walnuts in the cooking liquid, then spoon the cooking liquid and nuts over the bananas.
Serve hot with vanilla ice cream.
Optional flambe: Before dividing the bananas into individual dishes, pour 1 oz rum over the bananas and carefully ignite with a long-reach lighter. Wait until the flames burn off before serving, or extinguish by covering the dish with an ovenproof lid.