Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting

This deliciously decadent and technically accurate Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting is so good, it is impossible to resist!

Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting

What can I say about this delicious purple sweet potato cake? This was one of my most adventurous holiday recipes, but it produced the most rewarding dessert I ever had on my table! I just had to share it with you! This cake had been on my todo list for a while but I held off and had to do a lot of extensive research to ensure this purple sweet potato cake came out perfect with the right fluffy consistency and beautiful color, not to mention the addictive taste! This sweet potato cake with the marshmallow cream cheese frosting was honestly one of my best cake recipes to date (I know I seem to say that a lot but it’s honestly how I feel!). In fact the potato cake was so good i was unable to keep some leftovers for the next day! The making of this cake can get quite technical but no need to panic, yours truly is here to walk you through the process of getting this right all the time! I will first explain the key ingredients to a successful purple sweet potato cake before moving on to the recipe. This is not one of those recipes that you want to simply skip to the recipe. If you want to make this, please take a moment to read through the tips and reasons for selecting the right ingredients. You won’t regret it!!

Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting

There are two common types of purple sweet potatoes that can be found in most Asian supermarkets or traditional grocers. One of them is the Stokes purple sweet potato, pictured here on the left. It is characterized by its distinctively purple flesh and purple skin. It is the best textured sweet potato for this recipe as it is a little dry, and somewhat fibrous (similar to a russet potato) once it is cooked. It also keeps most of its vibrant color when cook and once baked into the cake.

Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting - Stokes purple vs okinawa purple

The other common purple sweet potato that you might think to use for this recipe is the Okinawan purple sweet potato pictured here on the right. Do not use the okinawan purple sweet potato in this recipe! As you can see there is quite a texture difference in these two sweet potatoes. The Okinawan sweet potato is creamy once cooked, and has a sweeter taste than the Stokes sweet potatoes. It also turns grey-blue once it is cooked, and when used in baking it can turn your baked goods blue.

Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting - Stokes purple blend vs okinawa purple blend

A good substitute for the Stokes purple sweet potato in this recipe is any sweet potato with a dry/starchy consistency similar to a russet potato when cooked such as the Hannah sweet potato (a sweet potato similar in texture to the Stokes with pale skin and yellowish flesh when cooked), the Japanese/kotobuki sweet potato, and the Jewel sweet potato (not to be confused with the garnet sweet potato that has a similar orange color when cooked, but is creamy in consistency).

The summary of this little story is that when seeking to substitute a sweet potato for this recipe, go with one that has a similar texture to the one used for this cake, and not just a similar color. The reason you need a sweet potato with a drier consistency is that the cake has quite a bit of moisture from its other ingredients, and using a creamy sweet potato will result in a gummy and dense textured cake… trust me, it has happened to me before.

Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting - The unveiling!!!

This cake turned out beautifully and tasted absolutely amazing with the marshmallow cream cheese frosting and the crushed walnuts and toasted mashed potato pieces.
Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting - Spotlight

5 from 4 votes
Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting
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Purple Sweet Potato Cake Recipe with Marshmallow Cream Cheese Frosting
Prep Time
20 mins
Cook Time
40 mins
Total Time
55 mins
 

This deliciously decadent and technically accurate Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting is so good, it is impossible to resist!

Servings: 15 servings
Calories: 442 kcal
Ingredients
Purple Sweet Potato Cake Sponge
  • 2 ¾ cups all purpose flour
  • 1 ½ cups sugar
  • 2 tsp baking powder
  • 1 tsp baking soda
  • 1 cup cooked mashed purple sweet potato (please read text for specification)
  • 1 cup milk
  • ¾ cup sour cream
  • 1⁄3 cup canola oil
  • 2 tsp vanilla extract
  • ½ tsp salt
  • few drops purple food coloring (optional)
Marshmallow Cream Cheese Frosting
  • 8 ounces cream cheese
  • 8 ounces butter (2 sticks)
  • 7 ounces marshmallow fluff
Instructions
  1. Grease and flour two 8 inch cake pans and set aside. 

  2. Preheat your oven to 350°F or 180°C

  3. Combine the flour, baking powder and baking soda and salt with a whisk and set aside. 

  4. Using a stick blender or in a blender, blend the mashed potatoes, milk sour cream canola oil, and vanilla extract until it is smooth and properly incorporated. Don't try to do this step with just a whisk, it will not mix evenly, and it is important that it does. If you want a more vibrant cake, add a few drops of purple food coloring, otherwise, skip it.  

  5. Combine the wet and the dry ingredients with a whisk until there are no lumps in the batter, and the cake is evenly mixed. Do not over mix!

  6. Split the cake mixture into the two prepared 8 inch cake pans, and bake in the preheated oven for 35-40 minutes or until a skewer inserted in the middle of the pan comes out clean.

  7. Allow to cool completely before frosting

To make the frosting
  1. Mix the cream cheese, butter, and marshmallow fluff in a mixer or with a hand mixer until it is well combined.

  2. Store in the refrigerator until ready to use.

  3. Simply assemble the cake as neatly or as rustic as you wish and decorate with leftover mashed potato pieces and toasted crushed walnuts.

Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting - Close up slice Purple Sweet Potato Cake with Marshmallow Cream Cheese Frosting - Overhead shot

I am so proud of how this purple sweet potato cake turned out and I know you will love it so….let me know how it goes when you make it! Also I’d like to know if you’ve tried other frostings outside of the marshmallow cream cheese frosting I used (which went so well with this cake, it is currently at the top of my favorite frostings list at the moment…right next to caramel). Feel free to also take a look at some of my other decadent cake recipes like my coconut caramel cake or my amazing black forest cake recipe. I hope you enjoy making this cake as much as I did!

18 Comments

  1. Ayobami

    December 5, 2017 at 10:05 am

    This looks stunning!!!

    Reply
    • Lois

      December 5, 2017 at 11:07 am

      Thank you so much Ayobami!!

      Reply
  2. Joy

    December 5, 2017 at 12:14 pm

    I’m in awe. You go Lois! 🙂

    Reply
    • Lois

      December 6, 2017 at 9:50 am

      Thanks Joy! That is quite high praise!

      Reply
  3. Lydia from Lydia's Flexitarian Kitchen

    December 6, 2017 at 6:57 am

    What gorgeous photos…and that marshmallow frosting! What a great idea to use that instead of a buttercream. I have to admit I was skeptical about the texture of the cake because where I’m from sweet potato biscuits are very dense instead of light and fluffy. Your demonstration of the difference between the two varieties explains why. The sweet potatoes common to my area are very creamy when cooked so naturally they will make a heavier product…now I’m wondering what purple sweet potato biscuits would be like.

    Reply
    • Lois

      December 6, 2017 at 11:04 am

      Right Lydia! I had sweet potato cake one time and the texture was divine, I tried recreating it and it came out really gummy and dense, but I kept trying and landed on this. I can only imagine what purple potato biscuits will taste look and taste like… yum!

      Reply
  4. Sarah

    December 6, 2017 at 5:19 pm

    Okay- I really want to try this!!! I’m obsessed with sweet potatoes, and I think this sounds AMAZING! Gorgeous photos.

    Reply
    • Lois

      December 7, 2017 at 8:56 am

      Thank you Sarah!

      Reply
  5. Dominique | Perchance to Cook

    December 6, 2017 at 5:53 pm

    Oh yuuuummm, what a show stopper! This cake is calling my name! It’s beautiful and sounds so incredibly flavorful.

    Reply
    • Lois

      December 7, 2017 at 8:57 am

      Thanks Dominique!

      Reply
  6. Christine

    December 7, 2017 at 10:36 pm

    Oh my goodness, this is gorgeous! That icing looks delicious. Love purple sweet potatoes!

    Reply
  7. Tina

    December 8, 2017 at 10:33 am

    I never would have thought to use sweet potatoes in a cake, what a GREAT idea! How fun, saving this for later.

    Reply
  8. Helene

    December 8, 2017 at 11:41 am

    We do get those sweet potato variety here!! =D
    you got me drooling and in awe with your cake. The color is so attractive and I bet if you have guests over that they would not believe that this decadent and delicious looking cake includes sweet potatoes as a main ingredient.

    Reply
    • Lois

      December 10, 2017 at 9:33 pm

      You are right, the few people that got to try it (or should I say devour it), did not believe it was made with sweet potato

      Reply
  9. Emily Leary

    December 9, 2017 at 2:01 pm

    WOW. Just look at the hue on that sponge. I think I’m in love. The flavours sound incredible too. I’m practically drooling on my screen here.

    Reply
  10. Abby @ WinsteadWandering

    December 9, 2017 at 7:26 pm

    The purple of this cake is gorgeous! My purple-obsessed five-year-old would love it. I’d just be over in the corner hoarding the frosting.

    Reply
  11. Lynette

    December 10, 2017 at 2:35 pm

    So pretty! I would never had guessed it had sweet potato in it if you hadn’t shared all the details.

    Reply
  12. Jessica Pinney

    December 10, 2017 at 4:59 pm

    Whoa, I’m lovin’ the color the purple sweet potato gives the cake. So pretty!

    Reply

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