Sweet Potato Sheet Cake with Marshmallow Frosting Recipe

If you have a soft spot for cozy, comforting desserts that bring a unique twist to family favorites, let me introduce you to the Sweet Potato Sheet Cake with Marshmallow Frosting. This delightful treat combines the natural sweetness and creamy texture of roasted sweet potatoes with a tender, spice-kissed cake base and a fluffy, toasted marshmallow topping that is simply irresistible. It’s a vibrant celebration of fall flavors in one gorgeous sheet cake, perfect for any occasion when you want to impress your friends or just treat yourself to something truly special.

Ingredients You’ll Need

Every ingredient in this recipe plays a crucial role, whether it’s contributing moisture, flavor, or that perfect tender crumb. The simplicity of the elements allows the rich sweetness of the sweet potatoes and warm spices to shine, while the marshmallow frosting adds a light, cloud-like finish that puts this cake over the top.

• Sweet potatoes (1 1/2 pounds): Roasted and pureed, they bring natural sweetness and an incredibly moist texture.
• Flour (2 1/2 cups): The foundation of the cake, providing structure; unbleached or gluten-free works great.
• Baking powder and baking soda (1 tsp each): Both agents help the cake rise beautifully, creating a light crumb.
• Cardamom and cinnamon (1 tsp each): Spices that infuse warm, aromatic depth, enhancing the sweet potato flavor.
• Salt (3/4 tsp): Just a pinch to balance the sweetness and boost all the flavors.
• Unsalted butter (16 tbsp): Melted for richness and tenderness in the cake.
• Granulated sugar (1 cup for cake, 1 1/4 cups for frosting): Sweetens the batter and the marshmallow topping.
• Orange juice (1/2 cup): Adds a subtle citrus brightness that complements the earthiness of the sweet potatoes.
• Eggs (2 yolks and 6 whites): Yolks enrich the cake, whites are whipped to fluffy perfection in the frosting.
• Vanilla extract (1 tsp for cake, 1 tbsp for frosting): Adds warmth and complexity to both elements.
• Natural yellow and red food coloring (optional): To enhance the cake’s beautiful orange hue.
• Cream of tartar or lemon juice (1/8 tsp): Stabilizes the delicate egg whites in the marshmallow frosting.
• Toasted pecans or walnuts (1/4 cup): Adds a delightful crunch and nuttiness as a garnish.
• Water (1 tbsp): Helps achieve a smooth sweet potato purée.

How to Make Sweet Potato Sheet Cake with Marshmallow Frosting

Step 1: Roast and Puree the Sweet Potatoes

Begin by piercing the sweet potatoes and baking them until soft and tender. This roasting step brings out their natural sugars and gives the cake that deep, rich flavor. Once cool enough to handle, peel and puree the flesh with a bit of water until smooth, setting aside exactly 1 3/4 cups to maintain perfect moisture balance in the batter.

Step 2: Prepare Your Baking Pan

Lightly grease a 9″ x 13″ pan, then line it with parchment paper, creating a sling for easy cake removal later. This little trick ensures your cake won’t stick and keeps cleanup easier, especially when handling a marshmallow-topped dessert.

Step 3: Mix the Dry Ingredients

In a separate bowl, whisk together flour, baking powder, baking soda, cardamom, cinnamon, and salt. Combining the dry ingredients first helps evenly distribute the leavening agents and spices throughout the cake, giving every bite a perfect, consistent flavor.

Step 4: Create the Cake Batter

Start with the melted butter and sugar in a large bowl, whisking until well combined. Then add your sweet potato purée, orange juice, egg yolks, vanilla, and optional food coloring. This creates a fragrant, colorful, and luscious base that is both moist and light. Carefully fold in the dry ingredients in two batches, maintaining the batter’s airiness.

Step 5: Incorporate Whipped Egg Whites

Whip the egg whites until foamy, then gently fold them into the batter until no white streaks remain. This step introduces essential air to the batter, ensuring your Sweet Potato Sheet Cake with Marshmallow Frosting is fluffy with a tender crumb, not dense or heavy.

Step 6: Bake to Perfection

Transfer the batter evenly into your prepared pan and bake at 350°F for about 35 to 40 minutes. When done, the center will be set and a toothpick inserted will come out clean. Let cool partially in the pan before using the parchment sling to transfer the cake to a wire rack to cool completely — the perfect base for our heavenly frosting.

Step 7: Make the Marshmallow Frosting

Combine sugar, egg whites, vanilla, salt, and cream of tartar in a heatproof bowl over simmering water while whisking constantly. When the sugar dissolves completely and the mixture reaches 161°F, remove from heat and beat with a mixer until stiff peaks form. This luscious, glossy frosting is the signature finish that makes this cake stand out.

Step 8: Assemble and Finish

Spread the marshmallow frosting evenly over the cooled cake using a spoon or spatula, then create whimsical swirls for that classic dessert look. Toast the topping lightly with a kitchen torch or under the broiler until golden edges form — watch closely to avoid burning. Finish off with a sprinkle of toasted nuts to add crunch and a nutty contrast.

How to Serve Sweet Potato Sheet Cake with Marshmallow Frosting

Garnishes

To complement the silky sweetness and spices in the cake, a simple sprinkle of toasted pecans or walnuts brings beautiful texture and a toasty note. For an extra festive touch, try adding a few delicate edible flowers or a dusting of cinnamon to elevate the presentation.

Side Dishes

This cake pairs wonderfully with a scoop of vanilla ice cream or a dollop of lightly whipped cream to balance its rich texture. A warm cup of spiced chai or black coffee also highlights its warm spice notes, making it an ideal dessert for a cozy gathering.

Creative Ways to Present

Serve the cake in rustic squares on wooden boards for casual entertaining, or dress it up with fresh fruit slices and mint leaves for a show-stopping centerpiece. For a playful twist, cut into mini squares and serve on sticks for a cake pop party treat that keeps everyone coming back for more.

Make Ahead and Storage

Storing Leftovers

Your leftover Sweet Potato Sheet Cake with Marshmallow Frosting should be covered tightly and kept at room temperature for up to three days to preserve the marshmallow topping’s delicate texture. Avoid refrigeration if possible, as it can cause the marshmallow frosting to weep or become sticky.

Freezing

If you need to freeze the cake, it’s best to freeze it without the marshmallow frosting. Wrap the cake tightly in plastic wrap, then foil, and freeze for up to two months. When ready to enjoy, thaw overnight in the refrigerator and frost fresh with homemade marshmallow topping for the best texture.

Reheating

Since this cake is best enjoyed fresh, if you want to warm a slice, place it in a warm oven (about 300°F) for a few minutes to soften without melting the marshmallow topping too much. Avoid microwaving as it might make the frosting gummy.

FAQs

Can I use canned sweet potato purée instead of roasting my own?

While canned purée can be a shortcut, roasting your own sweet potatoes develops a richer flavor and a better texture that really shines in this cake. If you do use canned, choose a high-quality brand with no added sugar or spices.

Is the marshmallow frosting safe to eat since it uses raw egg whites?

This frosting is safely cooked by whisking over simmering water until it reaches 161°F, which is hot enough to eliminate any risk from the raw egg whites, producing a smooth and safe marshmallow meringue topping.

Can I make this cake gluten-free?

Absolutely! Using a gluten-free measure-for-measure flour blend works beautifully here, ensuring you don’t miss out on the moist texture or flavor of the Sweet Potato Sheet Cake with Marshmallow Frosting.

How do I keep the marshmallow frosting from weeping?

Make sure you cook the sugar and egg mixture to the correct temperature and beat it until stiff peaks form, then refrigerate the cake if your environment is very warm. Also, serve the cake the same day for best results.

Can I make this cake ahead of time?

You can bake the cake a day in advance and store it tightly covered. For best texture, prepare and add the marshmallow frosting just before serving to impress everyone with that fresh, fluffy topping.

Final Thoughts

If you’re looking to add a little magic to your dessert table, the Sweet Potato Sheet Cake with Marshmallow Frosting is a showstopper that’s surprisingly easy to make and impossible not to love. From its moist, flavorful crumb to the luscious marshmallow swirls on top, this cake brings warmth and joy to every bite. I hope you give it a try soon — your taste buds will thank you!

Print