Arrange a rack in the middle position of oven.
Preheat your oven to 350 °F.
Grease a 5 x 9-inch loaf pan with cooking spray.
Ina medium bowl, add the flour, cocoa powder, baking soda, allspice and salt andwith a wire whisk, mix well.
In another large bowl, add the bananas and with a fork, mash well.
In the bowl of mashed bananas, add the butter and mix well.
Add the egg, brown sugar, and vanilla extract and beat until well combined.
Add the flour mixture and mix until just combined..
Fold in the chocolate chips.
Place the mixture into the prepared pan evenly.
Bake for about 1 hour.
Remove the pan of cake from oven and place onto a wire rack for about 5-10 minutes.
Then invert the cake onto the wire rack to cool completely before serving.
Cut the cake into desired-sized slices and serve.