In a large bowl, combine flour, cocoa powder, baking soda, baking powder, and salt.
Using an electric mixer, beat butter and sugar together until fluffy. With mixer on low speed, add eggs one at a time and then beat in bananas and vanilla extract.
Add flour mixture and stir until incorporated. Fold in chocolate chips.
Pour batter into prepared pan and bake 50 to 60 minutes, until toothpick comes out clean.
For glaze, in a small saucepan heat half-and-half and brown sugar until sugar dissolves and it just starts to simmer. Stir in butter and vanilla extract. Add chocolate chips, remove from heat, and let sit for 1 minute. Stir until smooth. Let glaze cool slightly and then drizzle on cooled bread.