In a medium bowl mash banana until smooth. Add in vanilla, maple syrup, beaten egg, and cooled coconut oil. In a separate bowl, mix the whole wheat pastry flour with the baking soda, salt, and cocoa powder. Add the dry ingredients into the wet and stir to combine, be careful not to overmix. Add to loaf tin (or two mini loaf tins) and bake on 350 degrees for about 30 minutes or until knife inserted in center comes out clean.