In a large bowl, mix together sourdough starter, honey, melted butter, and flour.
Cover and allow to ferment for 12-24 hours. If you want to skip the fermentation process, then proceed to the next step.
After the dough has fermented, preheat the oven to 350, place parchment paper in a loaf pan and uncover the bowl.
To the dough, add mashed banana, eggs, vanilla, salt, baking soda and baking powder. Mix together on low to medium speed until everything is combined well. Make sure to scrape the sides and bottom once or twice, then mix again.
Pour into a loaf pan and bake for 75-85 minutes until a toothpick or knife comes out clean when inserted into the loaf. If it starts to brown too much and it is not cooked through, cover with aluminum foil or parchment paper.
Take out of the oven and allow to cool for at least 10 minutes before slicing and enjoying.