Preheat your oven to 350 degrees and prepare a 9x5 loaf pan with parchment paper or nonstick spray.
In a large bowl, combine the butter, brown sugar, egg, and vanilla until smooth. Add banana and mix again.
In a separate large bowl, combine the flour, cocoa powder, baking soda, and salt.
Add the wet ingredients to the dry ingredients and combine well. Set aside.
In another large bowl, using a hand or stand mixer, mix the cream cheese, powdered sugar, vanilla, and egg.
Pour half of your chocolate banana mixture into the prepared loaf pan, and then add the cream cheese into the middle of it. Be careful not to spread the cream cheese to the edges; keep it in the center.
Pour the remaining chocolate banana mixture over the cream cheese, and then use a thin knife to gently swirl the cream cheese through the chocolate banana mix. Not too much, a swirl or two is enough.
Bake uncovered for 1 hour. If you touch the center of the loaf and it is not firm, bake 10 minutes longer or until the center is firm.
Once baked, remove from the oven. Let it cool in the loaf pan for 10 minutes, and then remove it from the pan and cool on a cooling rack completely.
While it's cooling, make the chocolate glaze. In a large microwave-safe bowl, melt the butter in your microwave on high for 1 minute or until hot and bubbly. Quickly add the chocolate chips and stir until melted and smooth. (You could also do this in a pot on the stove.)
Drizzle the chocolate glaze over the loaf and sprinkle with extra chocolate chips.
Slice and serve!