These subtly sweet and arguably healthy waffles are perfect for giving new life to leftover cooked sweet potatoes or neglected vegetable purees. I also highly recommend making a batch and freezing for easy kid friendly weekday breakfast. These are actually improved after freezing and a quick toast. No need to defrost first. Just pop a frozen waffle in your toaster at your preferred setting.

Makes ~6 waffles

What you need:

1 cup white all purpose flour
1 cup whole wheat all purpose flour
1 1/2 teaspoons baking soda
1/2 teaspoon salt
1 teaspoon ground cinnamon
1 teaspoon ground ginger
pinch of ground cloves
1 1/2 cup plain unsweetened kefir or drinkable yogurt
2 eggs, room temperature, separated
1 cup mashed cooked sweet potatoes
2 tablespoons maple syrup
1 teaspoon vanilla extract
6 tablespoons unsalted butter, melted, divided

What you do:

In a large bowl, whisk together the flours, baking soda, salt, cinnamon, ginger, and cloves.
In a medium bowl, whisk together yogurt, egg yolks, sweet potatoes, maple syrup and vanilla. Add most of the butter (reserving about 1 tablespoon for brushing the waffle iron) and whisk swiftly.
Add the wet ingredients to the dry and mix in a few swift strokes with a rubber spatula. It's okay if some of the dry ingredients are not fully incorporated. Do not over mix.
Heat up your waffle iron. While it is heating, with a whisk or electric mixer, beat the egg whites until stiff peaks form.
Gently fold the egg whites into the batter. Do not over mix. You are done when you see small pieces of whites speckling the batter.
Brush both sides of waffle iron with melted butter. Scoop about 1/3 cup of batter onto the waffle iron leaving room for spread. Cook 4-5 minutes or according to the setting of your iron. Serve immediately with maple syrup or keep warm in a low oven.
Freezer tip: cool on a wire rack before transferring to a freezer safe container.

Notes:

Change the spices to suit your taste. Feel free to use more or less cinnamon, ginger, or cloves, remove altogether or add other spices like nutmeg.
My vegetable mash of choice for waffles is the flesh (skins discarded) of oven baked/roasted sweet potatoes, but other roasted and steamed vegetables and fruits substitute nicely. Try squash, pumpkin, carrots, beets, apples or combination. See my note in the Shopping in Your Freezer post regarding using what you have.
If you don't have kefir or drinkable yogurt, you can use about 5+ oz plain Greek yogurt whisked together with enough milk to make 1 1/2 cups of thick liquid. Buttermilk also works.