Technically yes, but you won't have the same results. It can be really frustrating if you want to have waffles for breakfast and then you read through the recipe and discover that you need to wait for 12 hours - Ugh! Sourdough really excels when it's given a time to ferment and create lots of air bubbles. This is what will give the waffles just an airy and light texture. The time will also give the waffles a pleasant tart flavor from the sourdough. Even though you can still make the batter, make the "sponge" and then just add the remaining ingredients right away and make your waffles, they will be much more dense and not as delicious. If you want waffles right away, I recommend you use my Belgian Waffle recipe - no waiting or sourdough starter required.