Preheat an oven to 350 degrees. Grease or parchment line a 9x9 baking pan and set aside.
Using a mixer combine the bananas, agave, egg, vanilla and buttermilk. Blend well. In a second bowl mix the dry ingredients other than the chocolate chips and coconut.
Using the mixer add the dry ingredients to the wet mixing thoroughly. Then gently fold in the coconut and chocolate chips. Pour the batter into the greased baking pan.
Mix the ingredients for the dark chocolate streusel and crumble it across the top of the coffee cake. Bake for 45-55 minutes. Until a toothpick inserted in the center comes out clean.
Allow to rest until cool before removing from the pan and slicing.