First make the "sponge" which is going to ferment overnight: In large non-reactive mixing bowl combine the flours, unfed sourdough starter, honey or maple syrup, and buttermilk. Cover and let the batter rest overnight at room temperature (see NOTE below).
The following morning the batter will be nice and bubbly.Add the eggs, melted butter, salt and vanilla extract and beat just until combined. Use the batter immediately. Scoop out the batter and place it on a hot waffle iron. Cook the waffles in the waffle iron according to the manufacturer's instructions. Serve immediately with butter and syrup of your choice.
Notes
Fermentation: Fermenting the batter results in a tangier flavor which you may or may not be used to. Though I recommend fermenting the batter for its health benefits, if you prefer you can skip the fermentation process. Here's how: Instead of using unfed sourdough starter use active/fed sourdough starter and let the batter sit at room temperature for about an hour, then proceed with cooking.