Mash the Bananas: In a mixing bowl, mash the ripe bananas with a fork until completely smooth and creamy.

Mix Wet Ingredients: Add the melted butter, vanilla extract, sugar, and beaten egg to the mashed bananas. Stir everything together until well combined and smooth.

Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, and salt until evenly mixed.

Fold Everything Together: Gradually add the dry ingredients to the wet banana mixture, stirring gently just until combined. Be careful not to overmix, as this can make the bread dense. If using walnuts or chocolate chips, fold them into the batter at this stage.

Pour into Rice Cooker: Lightly grease the inner pot of your rice cooker, then pour the batter into the pot, spreading it out evenly.

Cook: Close the rice cooker lid and set it to the 'white rice' setting. Allow it to cook for 60 to 70 minutes, or until a toothpick inserted into the center of the bread comes out clean.

Cool and Slice: Once cooking is complete, carefully remove the bread from the rice cooker. Let it cool in the pot for about 10 minutes, then transfer it to a wire rack to cool completely before slicing and serving.