Preheat oven to 350F. Grease and flour a 9" x 5" loaf pan (I use homemade cake release). Line with parchment (optional).
In a small bowl, whisk together flour, cocoa powder, baking soda, and salt. Set aside.**
In a medium bowl, whisk together mashed bananas, oil, sugar, egg, and vanilla.
Add dry ingredients to wet and mix until combined. Fold in chocolate chips.
Bake for 55-65 mins or until a cake tester comes out mostly clean.
Cool in pan on wire rack for 10mins, turn out and cool completely on wire rack.
Finely chop chocolate and place into a bowl. Bring cream just barely to a simmer and pour over chopped chocolate. Cover with plastic wrap and let stand 2 mins. Stir with a spatula until combined and smooth.
Cool completely before drizzling over loaf.***
*This bread is not super sweet and has a strong chocolate flavour. If you'd like to tone that down and prefer it sweeter, reduce the cocoa powder to 1/4 cup and increase the flour to 1 1/4 cups.**One-bowl method - Skip this part and just add the dry right into the wet.***I had leftover ganache stored in the fridge that I zapped in the microwave for 30 seconds.