Overnight sponge:
120g levain, unfed
60g all-purpose flour
120g whole grain flour
224g buttermilk (or kefir)
60g water
6g raw sugar

Batter:
Sponge from above
7g sugar
1 large egg (50g)
56g neutral oil
2g vanilla
3g salt
6g baking soda

Mix sponge overnight. In the morning, mix batter. Rest 15 minutes as the waffle iron is heating. 
Spray waffle griddle with oil. Make waffles, careful to not overfill iron.