Preheat oven to 350 degrees Fahrenheit. Prepare a standard 9X5 loaf pan with shortening (or oil) and flour.
Melt butter in a mixing bowl.
Add the sugar, egg, and vanilla, and mix well.
In a separate bowl, combine the flour, baking soda, and salt (and cinnamon, if using).
Add the dry ingredients to the wet ingredients, a little at a time, mixing just until smooth.
Stir in the sour cream and bananas (and walnuts and/or chocolate chips, if using).
Pour into the prepared baking pan.
Bake for about 50 minutes, or just until a knife inserted in the middle comes out clean.
Cool the loaf 10-15 minutes, then loosen with a knife around the edges before turning out the loaf.
Enjoy!