St. Patrick’s Day Chocolate Cake

chocolate potato cake

I love potatoes so much that if I were to list the ways I eat them, I would sound a lot like Bubba in Forrest Gump:

Anyway, like I was sayin’, potatoes are the fruit of the earth. You can fry them, bake them, boil them. There’s uh, potato salad, mashed potatoes, screaming potatoes, potato pancakes, potato bread, potato dumplings, potato sticks, potato gratin, criss-cut fries, cream of potato soup, potato curry and potato cake. That—that’s about it.

By cake, I don’t mean latkes. I mean dessert. Mashed potatoes make moist bread, like Nutella babka, but I’d never tried it in cake. I wanted to add it to a favorite chocolate cake recipe, but I wasn’t sure whether it would replace the fat or the flour (because it’s creamy and starchy). Off to the Internet I searched. Some recipes had virtually no chocolate, while others had too much butter. This one, from I Love Chocolate, seemed the most reasonable. Since I didn’t have the Dutch-process cocoa it called for, I used natural cocoa and tinkered with the leavening. Besides, I think natural cocoa has a more complex flavor.

The resulting cake was light and moist. I didn’t think it was chocolatey enough, but maybe it’s because I forgot to add the vanilla. Paired with vegan chocolate frosting, this cake will cause tasters to do a double take. It’s an unusual dessert for St. Patrick’s Day, because it doesn’t scream green (or Guinness). If you really want to go green though, has plenty of ideas, like apple celery granita.

Irish Chocolate-Potato Cake

Cake adapted from Stephanie Zonis. Frosting adapted from More Great Good Dairy-Free Desserts Naturally by Fran Costigan.

For cake:
2 medium or 1 large potato (to make 1 cup hot, unseasoned mashed potatoes)
2 tsp instant espresso or coffee granules, dissolved in 1 cup hot water
2 cups sifted all-purpose flour
3/4 cup unsweetened natural cocoa powder (not Dutch-processed)
2 tsp plus a pinch of baking soda
1/2 tsp salt
1 stick plus 2 tablespoons unsalted butter, softened
2 cups granulated sugar
1 tsp vanilla extract
4 large eggs

For frosting:
(Makes 2 cups, enough to fill and frost one 9-inch two-layer cake)
Tofu frosting without chocolate is too watery and beany for my tastes. This one, which resembles mousse, is a keeper.

1 (12.3-ounce) aseptic box firm silken tofu (recommended brand: Morinu)
1 tablespoon plus 1 tsp canola oil
1/3 tsp salt
1/4 cup sugar
1/4 cup unsweetened cocoa
1 heaping tsp vanilla extract
6 ounces (about 1 cup) semisweet or bittersweet chocolate, melted
1-3 tablespoons chocolate, vanilla, or plain soymilk, if needed

Equipment: potato ricer/food mill or a fine-mesh sieve, food processor, 9-inch round cake pan, serrated knife, icing spatula

Make mashed potatoes: Boil or steam the potatoes until fork tender, about 15 minutes. When the potatoes are cool enough to handle, peel off the skin. Pass the potatoes through a potato ricer/food mill. Or mash them with a fork and push the mixture through a fine-mesh sieve to get rid of the lumps. (You can make the mashed potatoes a couple days ahead of time.)

Make cake: Position a rack to center of the oven; preheat oven to 350°Â F. Grease 9-inch round pan with butter. Lightly flour the pan, knocking out any excess flour; set aside.

Place mashed potatoes into a medium bowl. With a small whisk, gradually stir in coffee to form a smooth mixture; do not beat mixture excessively. Cool to lukewarm.

Meanwhile, sift together flour, cocoa powder, baking soda and salt. Set aside.

In large bowl, combine the butter, sugar and vanilla with an electric mixer. Beat at a low speed to blend, then beat 2 minutes at medium speed, scraping down bowl and beater(s) with rubber spatula once or twice. Add eggs, 2 at a time, beating in at a low speed until blended. Scrape bowl and beater(s) with rubber spatula. Increase mixer speed to medium; beat 1 minute.

At lowest speed, add sifted dry ingredients in 3 additions and mashed potato-coffee mixture in two additions, beginning and ending with dry ingredients and beating after each addition just until blended. Scrape bowl and beater(s) occasionally with rubber spatula. Batter may still appear curdled after all ingredients have been added.

Pour batter into prepared pan and spread evenly. Bake in preheated oven about 1 hr, rotating pan 180 degrees during baking. Cake is done when toothpick inserted near center emerges with a few moist crumbs still clinging to it. Remove to cooling rack.

During baking, cake center will rise higher than edges, but center will fall slightly as cake cools. Cool completely before frosting. Store at room temperature, covered airtight, for up to 3 days; freeze for longer storage.

vegan chocolate frosting

Make frosting: Combine the drained tofu, oil, and salt in a food processor, and process about 1 minute until pureed. Use a rubber spatula to clean the sides of the bowl and add the sugar, cocoa, and vanilla. Process 1 to 2 minutes, until the tofu mixture is smooth.

Add the melted chocolate and pulse the processor three or four times to incorporate. Process 1 to 2 minutes until the mixture is very creamy. Refrigerate in the processor for 20 minutes. The cream may need to chill for 1 to 6 hours in order for it to become firm enough to spread.

The degree of firmness will determine the amount of soy milk needed to create the final texture. It should be thick but easy to spread. Dip an icing spatula into the cream to test to the texture. If the cream is too stiff to use, add 3 tablespoons of the soy milk and process 1 minute. Add more soy milk, 1 tablespoon at a time as needed. When the cream is ready to use, spoon it into a bowl and begin to assemble the cake.

Frost the cake: With a serrated knife, level off the top of the cake. Cut the cake into two even layers. (Need more detailed instructions?) Cover one layer with frosting, then add the top layer. Frost the top and sides.

finished chocolate cake

Comments (15)      Email Email      Print Print


  1. Katie said,

    That looks wonderful. I haven’t had potato in a cake before but yours looks so good I now want to give it a go.

    March 14, 2008 at 2:02 am

  2. jen of a2eatwrite said,

    This looks remarkable. Gorgeous pics, too!

    March 14, 2008 at 7:38 am

  3. Nick said,

    Delicious looking and not entirely unhealthy. I’ve heard of using baked potatoes in baking, I really need to try that. If nothing else, the frosting looks deadly. I think I might make a batch of the frosting and just eat that!

    The Peanut Butter Boy

    March 14, 2008 at 8:40 pm

  4. Indigo said,

    That photo of the swirly chocolate goo in your food processor makes me want to marry you, just a little bit.

    You, or your cake. I’m not fussy.

    March 15, 2008 at 3:06 pm

  5. Fran Costigan said,

    Hi Jessica,
    I’m very happy to see the Chocolate Cream Frosting from my book, Great Good Dairy Free Desserts Naturally, applied so handsomely on your moist sounding cake. Thank you for the attribution.

    Though I know longer use dairy, eggs, or refined sugar, I do know a good cake when I see one. I agree with you that desserts should be good for you, and must taste good too. Funny enough, I get lots of marriage proposals via my Chocolate Cake to Live For.

    Next time you might consider using my dairy free ganache. By the way, I have used water ganache, though it amazes me still. My DF ganache, made with either soy creamer or coconut milk, produces a great glaze and truffle base. It’s all about the chocolate, of course.

    Happy St Pats to you.

    March 15, 2008 at 3:28 pm

  6. Jessica "Su Good Sweets" said,

    Fran, oh my goodness, the baker herself! I really like the vegan ganache frosting from Cook’s Illustrated (they were used to make the truffles in the header), but it’s loaded with chocolate and coconut milk. Your chocolate frosting was very close, but a fraction of the calories. I’ll keep your dairy-free ganache in mind, although I’m wary of soy creamer. It seems unnatural. Could I just add oil to soy milk?

    Indigo, you do realize that I’m a girl, right? Ha ha! Actually, when I served this cake last night, a guy wanted to kiss me and marry me. I said, “It’s just a cake. No, it’s just tofu and potatoes!”

    Nick, I think the frosting would be very good with peanut butter. To answer your question about the black-eyed bean cake, it is VERY moist. It’s like carrot cake without the carrots.

    March 15, 2008 at 10:22 pm

  7. Fran Costigan said,

    Hi Jessica
    You do not have to add oil; using soymilk works just fine in truffles.
    It makes sense that full-fat soymilk would be best but any (I use Silk) is fine.
    Re: the Peanut Butter remark: the recipe for my Chocolate Peanut Butter Cream, (also from More Great Good Desserts Naturally), is posted in my website. It answered my desire for you know whose Peanut Butter Cups.

    Eating chocolate everyday (but fairtraded and organic, I am Fran.

    March 16, 2008 at 8:38 am

  8. Nick said,

    I think I might try a version of the icing with peanut butter. I’m thinking of putting it on some homemade black bean brownies that I’ll be making soon! This bean puree thing is spreading over the internet like crazy since the start of the new year (new year resolutions maybe?). I remember searching for black bean brownies at the end of 2007 and read in a few places to buy a brownie mix from the store and just add a can of pureed black beans and nothing else. But now people are coming up with some really healthy recipes, some don’t even contain flour.

    I’m lovin this blog, its going on my blogroll right now! Thanks!

    The Peanut Butter Boy

    March 16, 2008 at 3:17 pm

  9. amanda said,

    Jess, this cake is absolutely amazing! I’ve never heard of potatoes in a cake, but if you can bake with beets, then you can bake with potatoes, right? the frosting on that cake looks really thick and smooth.

    March 17, 2008 at 12:01 am

  10. niko said,


    Another awesome creation that you have featured on your site that I have to try and make in my micro kitchen. Very cool. Gotta get to that Meme thing too.


    March 18, 2008 at 10:32 am

  11. DoughGirl said,

    What a wonderful cake from a wonderful baker….I’ve fallen in love with this blog! I’ll have to give this recipe a try!

    March 21, 2008 at 2:27 pm

  12. iamjuan said,

    I also LOVE potatoes, and your chocolate cake is ingenious. I will definitely give this a try!

    September 18, 2009 at 3:05 pm

  13. Margo said,

    I’m with you on potatoes! I love this cake and and I’m definitely going to try it. Thanks for posting this.

    March 12, 2012 at 12:12 pm

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