Grease and flour 8 nonstick rectangle carbon steel muffin pan (5.5*9cm) or 8*5 inch loaf pan.
In a separate bowl combine the flour, salt, and baking soda then sifted.
Cream together the butter with sugar. Add egg, and rum (vanilla). Mix in the condensed milk, sourdough starter and mashed bananas.
Add the flour mixture to banana mixture and mix just until combined. Do not over-mix. (Or you will have tough bread!)
Pour the batter into a greased 9x5-inch bread pan. Bake at 350F for 40-45 minutes or until a toothpick inserted into the center of the loaf comes out clean.
Cool completely prior to slicing.
So moist and yummy!
