Boxed Cake Mix with Sourdough Discard: A Complete Recipe

If you’ve got a cake mix on hand, as well as half a cup of sourdough discard, you can whip up a cake that’s delicious, moist, and aerated with that lovely “bounce’ you see in sourdough bread. Keep reading for the recipe! 

Can I Doctor a Cake Mix with Sourdough Discard? 

I know, I know. I come up with some strange ideas! But I was looking through my stash of cake mixes and pulled out a box of yellow cake. I had plenty of discard in the fridge. And you guys know me pretty well by now. I’m always looking for more (unusual) ways to doctor a box of cake mix. 

So, I decided to go for it. I had absolutely no idea if it would work. I’ve never seen another post about adding discard to a boxed cake mix. But, the risk was low: my cake mix was only $1.37 and the discard was just sitting there in my fridge, waiting to be used. 

How does sourdough starter discard affect baked goods? 

Let’s start with the assumption that you’re going to use ½ cup of discard in your cake. It’s half water, half flour. So, you will need to adjust your recipe to accommodate. 

In my case, I decided to pull back a little on the amount of moisture I was adding to my cake. Instead of a full cup of milk (my choice over water) I used ¾ cup. 

I knew that the discard would do four things: 

• Moisten the cake
• Help the cake stay fresher longer
• Add a slight “tang.’
• Result in slight texture changes
• Result in a lighter, tender crumb
• Add a bit of a lift
• Boost the flavor of the ingredients in the boxed mix

With all of those things in mind, I plowed forward, ready to get this experiment underway. And my, oh my! Am I ever glad I did. I knew, the moment I saw that baked cake, that I would love this one. (And I did! More on that later.) 

By the way, if you’re constantly looking for ways to use extra starter, be sure to browse my full collection of Sourdough Discard Recipes.

Let’s jump right in, friends. You can thank me later! 

Cake Mix with Sourdough Discard Ingredients

You will find a full printable recipe card at the bottom of this post.

• 1 yellow (or white) cake mix
• ¾ cup room temperature milk
• 3 room temperature eggs
• ½ cup oil or room temperature butter
• ½ cup room temperature sourdough discard (inactive) 

That’s it! Just a few brief ingredients

How to Make Sourdough Discard Cake

This comes together so easily, friends! 

Preheat oven to 325 degrees Fahrenheit. 

Prepare a bundt pan with Baker’s joy (or with shortening and flour)

Put the cake mix into a large bowl or the bowl of a stand mixer

Add oil (or butter) and eggs. 

Add starter and milk. 

Mix until thoroughly combined. 

The batter will look a bit different from your usual cake mix. It’s definitely thick and luscious. 

Scoop the batter into the pan and smooth until it’s level. 

Place in the preheated oven and bake for 50-55 minutes or until golden brown. A toothpick should come out clean. 

Remove the pan from the oven and place on a wire rack to cool. 

When you can handle the pan, flip the cake out. Continue to cool. 

You can dust the cake with powder sugar or use a glaze. I happened to have some cream cheese frosting on hand. I swirled it on, but then ended up spreading it out to melt all over the cake. I knew this would add a level of sweetness. 

Once cooled, slice and enjoy! 

Store the book in the fridge if you used a glaze with cream cheese like I did. Otherwise, you can leave it tightly covered at room temperature. It should stay fresh for 4-5 days, longer in the fridge. You can freeze this cake to eat later, if you prefer. 

What to Expect from This Cake

I had no idea if this experiment would work or not, but it most assuredly did! I loved the texture. I loved the flavor. I loved the ease. I loved the idea of adding some “ferment” to my mix. But most of all, I loved, loved, loved, the funny little air pockets the discard created on the outside of the cake. 

See those little light-colored spots? They’re the cake’s equivalent of a good sourdough bread’s air pockets. Even though my discard was inactive (and had been in the fridge for days) It will caused those lovely little pockets. That, of course, cause the cake to be light and luscious!

All in all, I would say this was a terrific idea and I’m so glad I came up with it! This blog is all about doctoring cake mixes and I’m thrilled to have one more way to do so. 

Variations on this Recipe

I’m already thinking of ways to add discard to other flavors of cake mix, friends. I happen to have some Dolly Parton Banana cake in my pantry. I’ve also got frozen bananas. I think I’ll make a banana bread next. (Yum!) 

Lemon would be another great option. I think the tang of the discard would pair beautifully with a lemon cake. I don’t happen to have a lemon cake mix on hand but I do have white cake and lots of fresh lemons. (Zest and juice for the win!) I’ll keep you posted on this one. 

Other Recipes to Enjoy

If you enjoy creative baking shortcuts like this, you’ll love my full guide on How to Doctor a Boxed Cake Mix, packed with simple upgrades.

For readers exploring sourdough baking, my Same-Day Sourdough Bread is a fantastic starting point.

And if you love transforming cake mixes, don’t miss my tutorial on How to Turn a Boxed Cake Mix into a Pound Cake.

Since this cake bakes beautifully in a Bundt pan, you might also enjoy my collection of Bundt Cake Recipes.

A few more, before you go:

• Banana Berry Cake
• Butter Pecan Pound Cake
• Pineapple Upside-Down Cake from a Boxed Mix
• Strawberry Lemonade Cake

That’s it for this post, friends!

I hope you enjoyed this delicious recipe. 

If you make this recipe and love it, don’t forget to leave a review and a comment below. And while you're at it, go ahead and pin some photos to your Pinterest boards!

Loved this recipe? Get more like it straight to your inbox. Sign up for our newsletter now!

Looking for my master list of sourdough discard recipes? I've got 'em--sweet, savory, breakfast items, and breads!

About the Author

Janice Thompson is an author, baker, and all-around mischief maker! She has overcome a host of baking catastrophes, including a toppled wedding cake, to learn more about the baking process. Janice has published over 165 books for the Christian market but particularly enjoys writing recipes and baking devotions. To learn more about Janice or to drop her a note, visit her About the Author page.