Preheat the oven to 350 F. Grease a 8” X 4” loaf pan and line with wax paper and set aside.
Mix the milk and vinegar together and set aside for at least 5 minutes. The milk will curdle and become sour. The sour milk makes this banana bread moist.
Whisk the eggs and sugar together.
Add the oil and sour milk to the batter and mix well.
Add the mashed bananas and mix.
Sift the flour, flax seed meal, and salt and add it to the mixture and mix until the batter is smooth.
Stir in the vanilla and chopped nuts.
Fold the baking soda into the batter until no lumps are left.
Pour 1/3 of the batter into a loaf pan. Then drizzle some of the melted chocolate over it.
Repeat with the remaining batter and melted chocolate. Leave some chocolate to drizzle on top of the bread so it forms a crust after baking.
If you want, add some walnuts to the top of the bread.
Bake it for 50 minutes or until a toothpick comes out clean.