The idea of putting potatoes in a cake might sound unusual at first, but this Chocolate Potato Cake will completely change your perspective on what makes a dessert extraordinary. The secret ingredient of mashed potatoes creates an incredibly moist, tender crumb that stays fresh for days, while adding virtually no potato flavor at all. Instead, the potatoes work their magic behind the scenes, creating a cake so rich and fudgy that nobody would ever guess the secret unless you told them. This chocolate cake is deeply flavored with cocoa, perfectly sweetened, and has a texture that’s somewhere between a classic layer cake and a dense brownie. It’s an old-fashioned recipe that’s been passed down through generations, born from resourcefulness during times when ingredients were scarce, but beloved today simply because it produces one of the most delicious chocolate cakes you’ll ever taste. Perfect for birthdays, potlucks, or any time you want to impress with both flavor and an interesting conversation starter.
Serving Quantity: 12 servings
Cooking Time: 35 minutes (plus 1 hour cooling time and 30 minutes prep time)
Nutrition Information (per serving):
- Calories: 385
- Protein: 5g
- Fat: 18g
- Carbohydrates: 54g
- Fiber: 3g
- Sugar: 38g
- Sodium: 320mg
1. Gather Your Ingredients
For the cake:
- One cup mashed potatoes (about 2 medium potatoes, freshly cooked and mashed)
- Two cups all-purpose flour
- Two cups granulated sugar
- Three-quarters cup unsweetened cocoa powder
- Two teaspoons baking soda
- One teaspoon baking powder
- One teaspoon salt
- One cup buttermilk, room temperature
- One cup hot brewed coffee (or hot water)
- Half cup vegetable oil
- Two large eggs, room temperature
- Two teaspoons vanilla extract
For the chocolate frosting:
- Half cup unsalted butter, softened
- Two-thirds cup unsweetened cocoa powder
- Three cups powdered sugar
- One-third cup whole milk
- One teaspoon vanilla extract
- Pinch of salt
2. Prepare the Potatoes
Peel two medium russet or Yukon Gold potatoes and cut them into chunks about 1 inch in size. Place the potato chunks in a medium pot and cover with cold water by about 2 inches. Add a pinch of salt to the water. Bring to a boil over high heat, then reduce to medium and simmer for 15 to 20 minutes until the potatoes are completely tender when pierced with a fork. Drain the potatoes thoroughly in a colander and return them to the hot pot. Let them sit for a minute to allow excess moisture to evaporate. Mash the potatoes until completely smooth with no lumps remaining. You can use a potato masher, ricer, or electric mixer. Measure out exactly one cup of mashed potatoes and let them cool to room temperature before using. You can prepare the potatoes a day ahead and refrigerate them.
3. Prepare the Pans and Oven
Preheat your oven to 350 degrees Fahrenheit. Grease two 9-inch round cake pans thoroughly with butter or non-stick cooking spray. Line the bottoms with circles of parchment paper for extra insurance against sticking. Grease the parchment paper as well. Dust the pans lightly with cocoa powder, tapping out any excess. This prevents white flour marks on your chocolate cake and adds extra chocolate flavor to the edges. Alternatively, you can bake this as a 9-by-13-inch sheet cake in a single pan, which is easier but less impressive for presentations.
4. Mix the Dry Ingredients
In a large mixing bowl, sift together the flour, sugar, cocoa powder, baking soda, baking powder, and salt. Sifting is particularly important for cocoa powder as it tends to be lumpy and sifting ensures even distribution throughout the batter. Whisk the dry ingredients together thoroughly for about 30 seconds to ensure everything is evenly combined. The mixture should be a uniform dark brown color with no streaks of white flour visible. Set this bowl aside while you prepare the wet ingredients.
5. Combine the Wet Ingredients
In another large bowl or the bowl of a stand mixer, combine the cooled mashed potatoes, buttermilk, hot coffee, vegetable oil, eggs, and vanilla extract. Using an electric mixer on medium speed, beat everything together for about 2 minutes until well combined and relatively smooth. The mixture will look a bit unusual with the potatoes, but don’t worry, this is completely normal. The potatoes should be broken down and incorporated throughout the liquid. The hot coffee helps dissolve the cocoa powder and intensifies the chocolate flavor, so don’t skip it even though it seems like a lot of liquid.
6. Combine Wet and Dry Ingredients
Pour the wet ingredients into the bowl with the dry ingredients. Using the electric mixer on low speed, mix for about 30 seconds just until the flour is moistened. Scrape down the sides and bottom of the bowl with a rubber spatula to make sure no dry pockets remain. Continue mixing on medium speed for about 2 minutes until the batter is smooth, well combined, and slightly glossy. The batter will be quite thin and pourable, more like a thick liquid than a traditional cake batter. This is exactly what you want. The thin batter is what creates such a moist cake. Don’t worry if you see tiny specks of potato, they’ll disappear during baking.
7. Bake the Cake
Divide the batter evenly between the two prepared pans. Each pan should be about two-thirds full. Tap the pans gently on the counter a few times to release any air bubbles trapped in the batter. Place both pans on the middle rack of your preheated oven, spacing them several inches apart for even air circulation. Bake for 30 to 35 minutes. The cakes are done when a toothpick inserted into the center comes out with just a few moist crumbs attached, not wet batter. The tops should spring back when gently pressed, and the edges should be pulling away slightly from the sides of the pans. Don’t overbake or the cake will be dry.
8. Cool the Cakes
Remove the pans from the oven and place them on wire cooling racks. Let the cakes cool in the pans for exactly 15 minutes. This cooling time allows them to set up slightly so they won’t fall apart when removed. After 15 minutes, run a thin knife around the edge of each pan to loosen any stuck spots. Place a wire rack on top of one pan, flip everything over together, and gently lift off the pan. Peel off the parchment paper. Flip the cake right-side up onto another cooling rack. Repeat with the second cake. Let both cakes cool completely to room temperature before frosting, at least 1 hour. Frosting warm cake will cause the frosting to melt and slide off.
9. Make the Chocolate Frosting
In a large mixing bowl, beat the softened butter with an electric mixer on medium speed for about 1 minute until creamy and smooth. Add the cocoa powder and beat on low speed until combined, scraping down the sides as needed. Gradually add the powdered sugar one cup at a time, alternating with splashes of milk. Beat on low speed after each addition until incorporated. Once all the sugar and milk are added, add the vanilla extract and pinch of salt. Increase the mixer speed to medium-high and beat for about 3 minutes until the frosting is light, fluffy, and smooth. If the frosting seems too thick, add more milk one tablespoon at a time. If it’s too thin, add more powdered sugar a quarter cup at a time.
10. Assemble and Frost the Cake
Place one cake layer on your serving plate or cake stand. If the top is very domed, you can use a serrated knife to level it off for easier stacking, though this isn’t necessary. Spread about one cup of frosting evenly over the top of the first layer, spreading it all the way to the edges. Place the second cake layer on top, gently pressing down to adhere. Spread a thin layer of frosting over the entire cake, top and sides, to create a crumb coat that seals in any loose crumbs. Refrigerate for 15 minutes to set this layer. Then spread the remaining frosting generously over the top and sides of the cake, using an offset spatula to create swirls or a smooth finish as you prefer.
11. Serve and Store
Let the frosted cake sit at room temperature for about 30 minutes before slicing to allow the frosting to set slightly. Use a sharp knife dipped in hot water and wiped clean between each cut for the cleanest slices. This cake is incredibly moist and rich, so servings can be slightly smaller than you might cut for other cakes. Serve at room temperature for the best flavor and texture. Store leftover cake covered at room temperature for up to 3 days, or refrigerate for up to 5 days. The cake actually becomes more moist and flavorful after a day or two as the flavors meld together.
Tips for Perfect Results
- Use freshly cooked and mashed potatoes, not leftover mashed potatoes that contain butter, milk, or seasonings. Plain boiled and mashed potatoes work best.
- Make sure the mashed potatoes are completely smooth with absolutely no lumps. Lumpy potatoes will create pockets in your cake that don’t dissolve during baking.
- Let the mashed potatoes cool to room temperature before adding them to the batter. Hot potatoes can cook the eggs prematurely and create an uneven texture.
- Don’t skip the hot coffee. It doesn’t make the cake taste like coffee but rather intensifies the chocolate flavor. Hot water works as a substitute if you don’t drink coffee.
- The batter will be very thin and liquidy. This is correct and not a mistake. Resist any urge to add more flour to thicken it.
- Make sure all your dairy ingredients are at room temperature. Cold ingredients don’t combine as smoothly and can result in a less tender cake.
- For a sheet cake version, pour all the batter into a greased and cocoa-dusted 9-by-13-inch pan and bake for 35 to 40 minutes.
- The cake layers can be baked ahead and frozen for up to 3 months. Wrap them tightly in plastic wrap, then aluminum foil. Thaw overnight in the refrigerator before frosting.
- For an extra special touch, add chocolate chips, chopped nuts, or a layer of chocolate ganache between the layers along with the frosting.
- This cake stays incredibly moist for days, making it perfect for baking ahead for parties or events. The texture actually improves on the second and third day as the moisture from the potatoes continues to work its magic throughout the cake.
