Sweet Potato Muffins with Marshmallow Frosting

Dry mix:
1 cup whole wheat flour 
1 cup all-purpose flour
1/2 cup light or dark brown sugar, tightly packed 
1 tablespoons baking powder 
1/2 teaspoon salt
1 teaspoon cinnamon 
1/4 teaspoon ground ginger
Pinch freshly grated nutmeg 

Wet mix: 
1 cup whole milk 
2 large eggs
1/4 cup vegetable oil, plus 2 tablespoons 
1 teaspoon vanilla extract 
*1/2 cup sweet potato purée (from about 1 large sweet potato) 

Marshmallow Frosting: 
3 large egg whites
1 cup white granulated sugar
1/2 teaspoon cream of tartar
1/8 teaspoon salt  
3/4 teaspoon vanilla extract 

Special equipment: 
Electric Mixer
Double boiler or a heat-proof (stainless steel or glass) bowl that fits inside a medium saucepan 

1. Preheat the oven to 350 degrees F. In a medium bowl, mix together the dry ingredients: whole wheat flour, all-purpose, brown sugar, baking powder, salt, cinnamon, ginger, and nutmeg. 

2. In a measuring cup or bowl, measure out the milk; add the eggs, vegetable oil, vanilla extract and sweet potato purée. Beat the mixture together until thoroughly combined. Pour the wet ingredients into the dry ingredients and mix until just combined, being sure to not over mix the batter (this will result in tough muffins - and who wants tough muffins?). 

3. Line your muffin tins with liners and spray each muffin tin with cooking spray (they will stick to the muffin liners). Divide the batter between the muffin tins, filling each one about 3/4 of the way full. Transfer to the oven to bake for 20 to 25 minutes, or until a skewer comes out clean. Place on a cooling rack to cool completely before topping with icing. 

4. To make the frosting, add the egg whites, sugar, cream of tartar, salt and vanilla extract to a medium bowl. Place the bowl over a pot of simmering water, being sure the water doesn't touch the bottom of the bowl. Using an electric mixer, beat the mixture together until it becomes shiny, light and fluffy, about 5 to 7 minutes. (Yes, it actually takes that long so be sure to watch the clock.) When it's done, pour in the vanilla extract and beat until thoroughly mixed. Transfer the frosting to a piping bag with a star tip (or any tip of choice) attached and pipe the frosting onto the muffins. 

5. Using a kitchen torch, carefully scorch the tops until they're golden brown. Muffins should stay moist for up to 2 days if kept in an airtight container. 

*If you don't have sweet potato purée and would like to make your own for this recipes, here's what you do: Preheat the oven to 375 degrees F. Place the sweet potato on a baking sheet and roast for 30 to 40 minutes, until the sweet potato is tender when poked with a knife. Allow to cool completely. Peel the sweet potato and run its flesh through a potato ricer. Proceed with the recipe. 

Yields 12 muffins