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sweet potato cake with marshmallow frosting that has been toasted with a blow torch. top down image styled with a knife that has marshmallow meringue on the tip.
Heather Wolf

Sweet Potato Cake with Marshmallow Meringue

5 from 11 votes
Sweet Potato Cake with Marshmallow Meringue is a pillowy soft slice of heaven. Perfectly seasoned with your favorite fall spices, this sheet cake is topped with a thick layer of homemade marshmallow frosting.
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Prep Time 45 minutes
Cook Time 30 minutes
Marshmallow Meringue 25 minutes
Total Time 1 hour 40 minutes
Servings: 12
Course: Cakes and Cupcakes
Cuisine: American
Ingredients Method

Ingredients
  

Sweet Potato Sheet Cake
  • 2 cups all-purpose flour unbleached
  • 2 tsp baking powder
  • 1 tsp baking soda
  • 3 tsp cinnamon
  • 1 tsp ginger
  • 1/2 tsp nutmeg
  • 3/4 tsp sea salt fine
  • 1 cup unsalted butter softened to room temperature
  • 1 cup dark brown sugar packed
  • 1/2 cup granulated sugar
  • 4 large eggs room temperature
  • 2 cups mashed sweet potatoes room temperature
  • 2 tsp vanilla extract pure
Marshmallow Meringue
  • 6 large egg whites
  • 1 1/2 cups granulated sugar
  • 3/4 tsp cream of tartar
  • 1 1/2 tsp vanilla extract pure
  • 1/8 tsp sea salt fine

Method
 

Sweet Potato Sheet Cake
  1. Preheat oven to 350 degrees. Grease and flour the bottom and sides of a 9 x 13 baking pan.
  2. In a large mixing bowl, whisk together flour, baking powder, baking soda, cinnamon, ginger, nutmeg and salt. Set aside.
  3. In a separate bowl, use and electric mixer to beat butter and both sugars until creamy smooth – approximately 2 to 3 minutes.
  4. Add eggs, one at a time, beating after each addition until incorporated. Scrape down the sides of the bowl with a spatula as needed.
  5. Beat in sweet potatoes and vanilla extract until smooth and lump free.
  6. Reduce mixer speed to low. Add dry ingredients to wet, beating until just combined. Take care to not overmix.
  7. Pour batter into baking pan then smooth the top with a spatula.
  8. Bake for 30 to 35 minutes or until a tester inserted into the center comes out with a few moist crumbs. Avoid overbaking.
  9. Remove pan from oven and place on a baking rack to cool completely before frosting.
Marshmallow Meringue
  1. Using a double boiler, bring an inch or two of water to a simmer. Continuously whisk egg whites and sugar over heat until sugar has completely dissolved, approximately 7 minutes.
  2. Immediately transfer marshmallow meringue to a clean mixing bowl and beat with an electric mixer until soft peaks form, approximately 5 minutes.
  3. Add cream of tarter, vanilla and salt and continue beating until stiff peaks form, approximately 10 to 12 minutes.
  4. Spread frosting onto cooled cake.
    *Note: this recipe makes a thick layer of meringue. If you prefer a thinner layer of frosting, cut the recipe in half.
  5. Toast marshmallow meringue with a blow torch until golden brown (or under an oven broiler for 1 to 2 minutes) until golden brown.
  6. Place cake in the refrigerator to chill until frosting sets then slice and serve.
  7. Note: Frosting will begin to wilt if left at room temperature. To prevent wilting, cover and chill cake in the refrigerator up to 2 days.