1) To make the starter: Measure 1 cup "fed" sourdough starter into a medium bowl.
2) Stir in the water and whole wheat flour, and mix until thoroughly combined.
3) Cover the bowl and set it aside for several hours, or up to overnight.
4) To make the batter: When you're ready to make the waffles, whisk the dry ingredients in a small bowl; you may need to sift the mixture if your cocoa is lumpy.
5) Add the dry ingredients, plus the eggs, melted butter, vanilla, and chocolate chips to the sourdough batter, stirring to combine.
6) To bake the waffles: Drop about ½ cup batter onto a greased, preheated waffle iron. Bake the waffle until steam stops coming out the sides of the iron. The waffles will feel soft and tender coming out of the iron, but will crisp up on standing.
7) Serve with sliced bananas, ice cream or whipped cream, and chocolate sauce, if desired.