Maybe we'll try this at Paul & Lyla's. I've made it at home with great results. Recipe from KAF Baker's Companion.
1 c unbleached AP flouw
1 c whole wheat flour
2 tsbp sugar
2 c buttermilk
1 c sourdough starter
1/4 c (1/2 stick) melted butter
3/4 tsp salt
1 tsp baking soda
First mix dry sponge ingredients together. Then mix in wet sponge ingredients til barely blended. Let rest overnight, or a few hours.
In a separate bowl, mix all batter ingredients together. Then blend with sponge until well incorporated.
Heat waffle iron, brush with canola or veg oil. Pour in 1 ladle full. Cook according to waffle iron directions, or until steam stops (about 6.5 minutes per waffle). Serve immediately, or keep warm in 200 deg. Leftovers freeze very nicely!