The secret to crispy sourdough waffles?
We regularly use the King Arthur Flour recipe, and consistently get waffles that are crispy on the outside, soft on the inside. A couple suggestions:


Make sure the waffle iron is completely preheated before adding the batter.
This recipe does need the waffles to cook for long enough; they'll be slightly dark. If you're only cooking them to a light golden, they aren't done enough.
Don't stack the waffles between cooking and serving, or the steam will make them soggy - put them in a single layer, and if you can't serve them immediately put them in a very low oven while you're making the rest of the waffles.