Preheat the oven to 350 degrees. Line a 8 x 8-inch baking pan with parchment paper. In a medium bowl, whisk the flour, baking powder, and salt together. Set aside.
In the bowl of your stand-type mixer, cream the butter and sugar together. Beat in the eggs and then the bananas and flavor.
Add the flour mixture and beat until just well combined, scraping down the sides of the bowl. Add the chips and walnuts.
Scrape the batter into the prepared pan. Bake for 25 minutes or until the cake tests done with a toothpick stuck in the center of the cake. Let cool on a rack in the pan.
Make the caramel sauce: Combine the butter, heavy cream and brown sugar in a small heavy saucepan; heat to boiling, stirring constantly. Boil gently over medium low heat until mixture is thickened, about 8 minutes. Preheat broiler. Spoon about 1/3 cup of the sauce over the pudding. Spread evenly on top. Place pudding under the broiler until the topping is bubbly, about 1 minute. Serve immediately spooned into dessert bowls. Drizzle with toffee sauce and top with sliced bananas and spoonful of whipped cream.