Preheat the waffle iron. Set it to medium-high. Give it time to heat fully. A hot iron equals crisp edges.

Mix the dry ingredients. In a large bowl, whisk flour, cornstarch, sugar, baking powder, baking soda, and salt until combined.

Whisk the wet ingredients. In another bowl, whisk eggs, milk, melted butter or oil, vanilla, and sourdough discard until mostly smooth. Some small lumps are fine.

Combine wet and dry. Pour the wet mixture into the dry. Stir gently until just combined. Do not overmix; a few streaks are okay.

Rest the batter 5–10 minutes. This helps hydrate the flour and lets the leavening kick in for a lighter waffle.

Grease the waffle iron. Lightly spray or brush with oil to prevent sticking.

Cook the waffles. Add batter to the iron (usually 1/3–1/2 cup for standard, 1/2–3/4 cup for Belgian). Close and cook until deep golden and crisp. Most irons take 3–5 minutes.

Hold the finished waffles. Place cooked waffles on a wire rack, not a plate. This keeps steam from softening the crust.

Serve hot with toppings. Butter and maple syrup are classics. Fresh berries, yogurt, nut butter, or a dusting of powdered sugar are all great.