In a large bowl, whisk together the flour, salt, and baking soda and set aside.
Melt the butter in the microwave for 45-60 seconds, stirring as needed. Let it cool slightly before using.
In a separate bowl, beat the melted butter, granulated sugar, and brown sugar until fullly combined (about 2-3 minutes).
Mash the bananas thoroughly and mix them into the batter. Beat in the eggs and the yolk one at a time until fully combined.
Mix in the sour cream and vanilla extract. Gently stir in the flour mixture just until combined. Fold in the chocolate chunks.
Preheat the oven to 325°F. Lightly grease and flour a standard loaf pan (9x5 or 8x4). Pour the batter into the pan and sprinkle some extra chocolate chunks on top. Bake for 1 hour or until the edges are a light golden brown and a toothpick inserted into the center comes out clean.
Let the loaf cool in the pan for 10-15 minutes. Then, transfer it to a wire rack to finish cooling. Once it's cooled, slice, serve, and enjoy!
Notes
Let the eggs and sour cream come to room temperature before adding them to the batter.
Salted butter provides the most flavor, but unsalted butter can also be used.
Let the melted butter cool slightly before adding it to the batter.
Measure the flour accurately by spooning it into a dry measuring cup and leveling it off with a straight edge.
Use extra-ripe bananas for the best flavor and texture.
Generally, 2-3 medium bananas will yield 1 cup mashed
Either a 9x5 or 8x4 loaf pan is recommended.
Line the pan with parchment paper for easy removal after baking.