Combine the sourdough starter, milk, and whole wheat flour together in a bowl. Cover and let sit overnight (at least 12 hours is ideal).
The next morning, beat the eggs and milk until frothy. Add in the vanilla extract and melted butter. Mix to combine.
Add the baking soda, cinnamon, ginger, nutmeg, and salt to the egg mixture.
Lastly, add the flour mixture in with the egg mixture. Stir gently until just combined.
Bake the waffles in a preheated waffle iron.
This recipe makes enough for 4-6 large waffles.