In a large bowl, whisk eggs until beaten. Add milk and vegetable oil and whisk to combine. Add sugars, sweet potato purée, and sourdough discard, and whisk until fully incorporated. Pour in the melted butter and stir until combined.
In a separate large bowl, whisk together flour, baking powder, salt, cinnamon, and nutmeg. Pour the wet ingredients into the dry ingredients. Stir until the batter is smooth (the batter may be slightly lumpy if you used mashed instead of puréed sweet potato).
Heat your waffle iron and brush with butter or spray with cooking spray. Pour batter (about ⅓ cup per waffle) on the iron and cook the waffles until golden brown. Serve immediately with your favorite toppings.
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Notes
Serving size: 2 waffles. Substitutions: You can also make these waffles using pumpkin purée or butternut squash purée for a different flavor profile. Keep in mind these options won't be as sweet as sweet potatoes. To make these waffles with active sourdough starter, replace the sourdough discard with active sourdough starter (200g).