Sourdough Brookies

If you’ve ever had trouble choosing between a fudgy brownie and a chewy chocolate chip cookie, sourdough brookies are about to become your new favorite bake. These indulgent bars combine the best of both worlds. Rich, chocolatey brownie on the bottom with golden, chewy cookie on top. The result? A dessert that’s gooey, decadent, and absolutely irresistible.

What makes these brookies extra special is the sourdough twist. Whether you’re using active starter or discard, the sourdough adds a subtle tang and depth of flavor that takes them far beyond your average brownie or cookie. Plus, it’s a fun and delicious way to make sure every bit of your sourdough starter gets put to good use.

Flat lay photo taken from above of sourdough brookies. There are two white plates with small pieces of sourdough brookies on it with small forks.

Why You’ll Love This Recipe

Two treats in one – the best of both worlds: rich sourdough brownies + chewy chocolate chip cookies for when you really can't decide!

Sourdough twist – adding sourdough starter to the two different batters not only enhances the flavor of these brookies, it also reduces food waste by helping you use up your sourdough discard.

Perfect for sharing – a crowd-pleaser for parties, bake sales, or a cozy weekend bake. They are so easy to slice up into individual pieces, perfect for packaging up to share!

A stack of 2 sourdough brookies sitting on a white plate.

Ingredients

Sourdough Starter (or Sourdough Discard) - That little scoop of starter (or discard) is what makes these brookies extra special. It adds a gentle tang, keeps things moist and chewy, and gives you a delicious way to use up that discard sitting on the counter.
Butter - Butter is the magic behind that rich, melt-in-your-mouth texture. It brings all the cozy bakery vibes and makes sure your brookies are fudgy and fabulous. As always, I'm using salted butter.
Sugar - Sweetness is key here! Sugar balances out the tang from the sourdough and helps lock in that soft, chewy texture we all love.
Eggs - Eggs are the glue that hold everything together. They add structure, moisture, and just the right amount of richness to keep every bite fudgy but firm. My eggs are large, if yours are smaller, use an extra egg!
Vanilla Extract - Think of vanilla as the flavor booster. It rounds everything out, giving warmth and sweetness that makes the chocolate shine even brighter.
All Purpose Flour
Baking Soda and Baking Powder - These little leavening helpers stop your brookies from turning into bricks. They give just enough lift to keep them soft but still satisfyingly dense.
Chocolate Chips - Little bursts of melty goodness! Chocolate chips make sure every bite is loaded with chocolatey joy—because you can never have too much. I'm using semi sweet chocolate chips.
Cocoa Powder - This is where the rich brownie flavor comes from. Cocoa powder adds that deep, chocolatey base that makes brookies what they are: the best of both worlds.
Salt - Don’t skip it! Salt makes the chocolate pop and balances all the sweetness. It’s the secret ingredient that makes everything taste better.

How To Make Sourdough Brookies

Making this delicious, sourdough treat is as simple as making a bowl of sourdough brownie batter and a bowl of sourdough chocolate chip cookie dough. It's really that easy! You'll need to bake this delicious sourdough dessert in a 9" x 13" baking pan.

Kate's Recipe Tips

I recommend making the sourdough chocolate chip cookie dough batter the day before you want to make these sourdough brookies and allow it to ferment in the fridge. Alternatively, you can place the brownie batter and chocolate chip cookie dough together in the baking pan and ferment together overnight.

Sourdough Chocolate Chip Cookie Dough Batter

Place the dry ingredients (flour, baking soda, salt and chocolate chips) into a large mixing bowl and combine. Set this aside.

Now in a separate bowl, combine sourdough starter, melted butter, brown sugar, white sugar, egg + egg yolk and vanilla extract. Stir together until they resemble runny caramel.

Now pour the wet ingredients into the dry ingredients and stir to form the cookie dough.

A bowl of sourdough chocolate chip cookie dough sitting on a counter top.

Cover the bowl with plastic wrap and place into the fridge for 12 to 24 hours.

Sourdough Brownie Batter

In a bowl, add the all purpose flour, white sugar, cocoa powder, salt and baking powder. Whisk the dry ingredients together until well combined.

Place the chocolate chips in the bowl and mix until they are all coated in the flour mixture.

On top of the dry ingredients, add the melted butter, 2 eggs, vanilla extract and sourdough starter.Using a spatula, gently mix all of the wet and dry ingredients together, ensuring that the sourdough starter is well combined (see notes for more info on this).This is a thick brownie mixture - that’s ok, it’s meant to be like this.

A bowl of sourdough brownie batter sitting on a white counter top with a bowl of sourdough chocolate chip cookie dough behind it.

Let's Make Sourdough Brookies

When you're ready to make your sourdough brookies, preheat your oven to 160C and lightly butter a 9" x 13" baking pan.

Spread the sourdough brownie batter evenly across the base of the pan so that the whole lot is covered with brownie.

A 9" x 13" tray of sourdough brownie batter.

Now, take your fermented sourdough chocolate chip cookie batter and place scoops of it all over the brownie batter until you've used up all of the chocolate chip cookie dough.

A tray of sourdough brookies ready to be baked in the oven.

Cover the pan with aluminum foil and place the baking pan into the oven to bake at 160C for around 25 minutes.

At the 25 minute mark, remove the aluminum foil and return the pan to the oven to bake uncovered for a further 35 minutes.

A tray of sourdough brookies that has just been baked and removed from the oven and placed on a wooden board.

Variations

Sourdough Peanut Butter Brookies – add blobs of peanut butter to the top of the cookie dough before baking the sourdough brookies.
Sourdough Mocha Brookies – add a few teaspoons of espresso powder to brownie batter. Instant coffee powder also works here, just dissolve it in a little hot water first.
Holiday Brookies – add crushed candy canes, M&Ms, or festive sprinkles to the top of the brookies before you bake them. I personally love the crushed candy canes which give them a peppermint flavor. So good!

Serving Ideas

I love eating these sourdough brookies just as they are, but you might also like to try these ideas:

Serve warm with a scoop of vanilla ice cream (seriously so good).
Pour a shot of espresso over a square of sourdough brookie and then top with vanilla whipped cream. Trust me on this one!
Cut into bite-sized squares for lunchboxes or parties. My boys love finding these in their lunchboxes!
Gift in a cute box or bag for neighbors and friends. You could even add them to a gorgeous festive cookie box, along with some sourdough ginger molasses cookies or spiced sourdough pecan cookies.

How To Store + Freeze

Store in an airtight container at room temp for 3–4 days. I find it's best to store whole if you can, rather than cut them as they tend to dry out if you cut them before storing them. You can refrigerate for up to a week for extra fudgy texture, but allow them to come to room temperature before you eat them. Alternatively, you can gently warm them in the microwave to bring out the fudgy texture.

Freeze individually wrapped slices for up to 3 months; thaw at room temp or warm in the oven.

Frequently Asked Questions

Can I use sourdough discard instead of active starter?

Absolutely, sourdough discard and active starter are interchangeable in sourdough discard recipes. Just make sure your discard isn't too old or sour.

Do I need to chill the cookie dough?

You don't have to, but I highly recommend it. The cookie dough is quite wet, so allowing it to chill down will not only allow your sourdough starter to ferment the cookie dough, it will also make it much easier to place onto the sourdough brownie batter.

Can I halve the recipe?

Absolutely you can halve the recipe. Another option is to make the recipe as is and then split it into two smaller baking pans (2 x 9" x 9" pans will work). That way you can have one for now and freeze the other one for another time.