To make the overnight sponge, stir down your refrigerated starter, and remove 1 cup (227g). Note: This is a good opportunity to feed the remainder, if necessary., In a large mixing bowl, stir together the 1 cup (227g) unfed starter, flour, sugar, and buttermilk., Cover and let rest at cool room temperature (about 65°F to 70°F) for about 12 hours, or overnight., In a small bowl or mixing cup, beat together the eggs, and oil or butter. Add to the overnight sponge., Add the salt and baking soda, stirring to combine. The batter will bubble., Pour batter onto your preheated, greased waffle iron, and bake according to the manufacturer's instructions., Serve waffles immediately, to ensure crispness. Or hold in a warm oven till ready to serve.