In a large mixing bowl, using a wooden spoon or whisk, mix butter into the mashed bananas.
Add peanut butter and stir until combined.
Mix in the sugar, egg, and vanilla.
Sprinkle the baking soda and salt over the mixture.
Add the flour and chocolate chips, mixing just until combined (all lumps of flour should be incorporated)
Pour mixture into a buttered 4-inch x 8-inch loaf pan.
Bake for 45-55 minutes, or until a toothpick or wooden skewer inserted into the center of the loaf comes out clean.
Transfer pan to a wire rack to cool for 15 minutes. Remove from pan and cool completely.
Use an offset spatula to apply as much chocolate ganache to the top of the bread as you'd like, then slice and serve.
Notes
The chocolate ganache will be liquid when you apply it, but it will set up and become more solid as it dries. Once the ganache has dried onto the bread, you can wrap any leftovers in plastic wrap or store them in an airtight container for up to 4 days.