Preheat oven to 350-Degrees F

• Place butter in a small bowl and cover with a napkin to avoid splatter. Microwave for 30 to 45 seconds.
• Crack eggs into a medium-sized bowl. Whisk vanilla into eggs until fluffy. Add melted butter, and whisk to combine.
• In a large bowl, whisk flour, sugar, baking soda, baking powder, salt, and cinnamon. If adding walnuts, chop and stir into the flour mixture.
• Stir the wet ingredients into the dry ingredients until combined. Fold the mashed bananas and blueberries or huckleberries into the batter. 
• Grease and flour a loaf pan, then pour batter into it. Bake loaf for 45 minutes then turn the temperature down to 325 and loosely cover with aluminum foil to avoid over-browning.
• Insert a toothpick into the center of the loaf. If done, the toothpick should come out clean. Insert a toothpick into the center of the loaf. If the toothpick is covered with wet batter, the banana bread needs to continue to cook. Check every 5 minutes until a toothpick comes out clean.
• Cool on the counter for approximately 15 minutes then carefully invert the loaf onto a wire rack. Cool completely before slicing.