Preheat your oven to 350°F (175°C) and grease a loaf pan.
In a large bowl, mash the ripe bananas until smooth.
Add the sourdough starter, melted butter, and brown sugar; mix well.
Stir in the egg and vanilla extract until fully incorporated.
In a separate bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Fold in any optional ingredients like nuts or chocolate chips.
Pour the batter into the prepared loaf pan and smooth the top.
Bake in the preheated oven for 50-60 minutes, or until a toothpick comes out clean.
Allow the bread to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.