Honestly, This Sourdough Discard Cake is a Family Legend

You know those late-night cravings when you remember you have that jar of Sourdough Discard crowding your fridge? This recipe was born right there, sandwiched between a midweek chocolate emergency and a desperate need to not waste another spoonful of starter. My dad’s got a real sweet tooth, and years ago, he suggested tossing some coconut in "just to see what would happen." Well, what happened was magic. Fudgy, dense, a touch tangy—all in a cake square that’s way too easy to keep nibbling ‘til it’s mysteriously vanished. I promise, this isn’t one of those snooty, fussy cakes—you’re basically one bowl away from chocolatey bliss (but don’t worry if you’re still in your pajamas)

Sourdough Discard Chocolate Coconut Cake Squares

Why I Keep Coming Back to This Cake (and My Family Will Riot If I Don't)

I make these cake squares basically any time my discard jar reaches “dangerously full” territory. The tang from the discard makes the chocolate pop, and honestly, the coconut is what seals the deal. My partner claims it’s like a Mounds bar and a brownie had a cute baby. Plus, it's speedy—the sort of thing you can throw together during a K-drama episode and still not miss the big plot twist. (And I’ll admit, there’s something so satisfying about sneaking a square straight from the tin when nobody’s looking.)

What Goes in These Squares? Here’s the Ingredient Lowdown:

1 cup (about 240g) sourdough discard (I use 100% hydration, but a little runnier or thicker works, don't overthink it)
¾ cup (150g) granulated sugar (sometimes I swap in coconut sugar if I’m feeling fancy, but regular sugar is my go-to)
⅔ cup (80g) unsweetened cocoa powder (Dutch-processed gives it that darker color, but any cocoa will do... my grandmother used Hershey's, let's be real)
½ cup (115g) melted butter (I’ve used coconut oil in a pinch—it works, though the flavor changes a bit)
2 large eggs
1 teaspoon vanilla extract (honestly, that imitation stuff does the trick if that’s what you’ve got)
½ teaspoon salt
1 cup (80g) shredded coconut (either sweetened or unsweetened—I can never remember which one I used last, and it’s always delicious)
½ cup (65g) all-purpose flour (on more than one occasion, I’ve left this out by accident; the cake still turns out, just gooier!)
1 teaspoon baking powder
½ cup (90g) chocolate chips (optional but, c’mon)

And if you REALLY want to make it special? Sprinkle a little flaky salt on top before baking. Learned that form my neighbour, June.

Let’s Bake! How to Make Sourdough Discard Chocolate Coconut Cake Squares

First things first, get your oven cranking up to 350°F (180°C). Grease or line an 8x8-inch baking pan with parchment paper (guess what, I ran out once and used foil—bit messy, still worked).
In a biggish bowl, whisk together the melted butter and sugar until it looks a bit like wet sand. Add in the eggs and vanilla; mix until glossy (this is where I usually sneak a taste and hope nobody sees).
Stir in the sourdough discard—don’t worry if it looks...odd. Mine always does.
Add cocoa powder and salt, then mix until just combined. Toss in the flour and baking powder, gently stirring (I sometimes overmix here, but it’s never ruined a batch).
Fold through the coconut and any chocolate chips (save a few for sprinkling on top because, well, why not?).
Scrape that glorious, sticky batter into your prepared pan; smooth the top (or at least try...it’s thick). Scatter reserved chips or a little extra coconut if you like jazzy tops.
Bake 25–30 minutes, until a toothpick in the center comes out with a little bit of goo on it (I check at 25 and usually can't wait longer). The edges will look set and shyly pulling away from the pan.
Let cool completely in the pan—if you can wait. Actually, a slightly warm square is pretty irresistible, but it cuts neater if you let it cool fully (I rarely do, but, ahem, you’ve been warned).

Notes I Learned the Hard Way

If your discard is super tangy, these will be delicious but might taste a tiny bit sharper—sometimes I bump up the sugar by a spoonful.
For extra gooey-ness, underbake by a couple of minutes. (But don’t go wild, unless you’re a risk taker! Learned that the slightly messy way.)
Coconut on the top browns FAST. Keep an eye out, especially if you’re daydreaming like me.

Variations I’ve Tried (and Yep, One Flop)

Swapped out half the coconut for chopped nuts—good crunch, but my kids called mutiny.
Tried subbing some of the flour with almond meal: turned out tasty but a bit more crumbly than I’d like (maybe needs more eggs?).
I tossed in dried cherries once and—well, it was a color clash but not bad if you like the sweet-and-tart thing.
Do not, and I repeat, do not use salted butter AND extra salt. Let’s just say the sea called and wanted its salt back.

Got Equipment? Or, What if You Don’t?

You really just need one mixing bowl, a whisk, and an 8x8" pan. I’ve made this with a fork and a Pyrex. If you’ve only got a 9x9-inch pan, just start checking for doneness at 22 minutes. And if you have only a loaf tin, it technically works—it just comes out taller and takes more time (and it feels like slicing bread. Cake bread? I dunno, but it’s still good).

How Long Do They Keep? Storage Reality Check

Supposedly, these keep in an airtight container for 3 days at room temp, a week in the fridge, or frozen up to 2 months. But honestly, in my house? If there’s any left after breakfast, it’s a miracle. They get a smidge denser after a day, which I actually love (don’t come at me, but the flavor deepens).

Want to Serve ‘em Like I Do?

Okay, here’s a trick we all love: a warm square with a scoop of vanilla ice cream and a big sprinkle of toasted coconut on top. Sometimes, I dust with cocoa powder if I’m feeling extra. For kids? They love them cold from the fridge, like cake candy bars.

The "If Only I’d Known" Pro Tips

I once dumped everything in at once then mixed—honestly, it still worked. But if you add the discard with the eggs, it gets lumpy. Stir gently, and you’re golden.
Letting it cool seems boring, but trust—if you want tidy squares, patience is a virtue. I rarely wait; I regret it every time.
Too much coconut on top is just inviting burnt bits. Less is more, as my Aunt Weezy would say.

Baker to Baker: Your Burning Questions

Can I use fed starter instead of discard? Totally, though the crumb might be a touch lighter. It’s forgiving!

What’s the best type of coconut? Unsweetened works best if you don’t fancy super-sweet treats. But, truth be told, anything from the back of your pantry is fair game.

Can I double the recipe? Oh, buddy—yes, but use a 9x13" pan and bake a bit longer. Or two pans, if you like washing up.

Does this freeze well? Yep, though the coconut can get a tiny bit icy. Wrap well and forget it’s there, then be excited later.

Can I make this dairy free? Sub coconut oil for butter and use dairy-free chips. I’ve actually done this for a friend, and no one even noticed.

Why does my cake sometimes sink in the middle? Usually means it needed a few more minutes or (oops) too much liquid in the discard. Still tastes brilliant, just got a bit more character!

That’s the lot, friend. Enjoy, make it yours, and if it flops, tell everyone you meant to make it a gooey pudding. Cheers!

Sourdough Discard Chocolate Coconut Cake Squares