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Sourdough Blondies

Sourdough Blondies! The perfect gooey blondie with a crackly crust is made even better with a dash of sourdough discard. These blondies have amazing butterscotch flavor.

three butterscotch blondies on a plate sprinkled with sugar

These blondies are nice and rich, but with a surprisingly light crumb thanks to a little lift from the natural yeast in the sourdough starter.

But wait, there’s more…

The discard also enhances the flavor of the blondie. There’s a slight background tang that is the perfect counterpart to the sweet butterscotch flavor. It’s so, so good.

If you don’t have one, check out my post to learn How to Make a Sourdough Starter. Then check out my system to Feed and Maintain Sourdough Starter or How to Keep a Small Starter.

Scroll through the step by step photos to see how to make Sourdough Blondies:

three process shots showing how to mix sourdough blondie batter
Vigorously stir the eggs in to the batter, then fold the discard into the batter until it’s almost combined.
two images showing how to fold flour into sourdough blondies
Fold the flour into the batter
two photos showing sourdough blondies before and after baking
Line the baking pan with parchment to make it easy to lift the blondies out of the pan.

Tips for making and storing Sourdough Blondies:

  • The recipe can be halved and baked in an 8″ or 9″ square pan.
  • Unfed sourdough starter will add a tangy flavor to the batter. I got great results with a starter that had been in the refrigerator, unfed, for about a week.
  • Butter the pan and line with parchment paper. This not only prevents sticking, it makes it much easier to lift the blondies out of the pan.
  • Stirring the batter vigorously after adding the eggs will incorporate air into the batter. As the blondies bake the bubbles rise to the surface and help form the crust. If you prefer a soft top on your blondies, you can skip that step.
  • Cool the blondies in the pan then use the parchment to transfer them to a cutting board.
  • To appreciate the subtle tangy flavor, I prefer to serve these spectacular blondies without any frosting
  • The blondies will keep at room temperature for several days.
  • Leftover blondies can be frozen. Layer them with parchment paper or plastic wrap to prevent them from sticking together. They’re delicious straight from the freezer or defrosted.

You might also like these other Blondie recipes, Classic Blondies, Butterscotch Ripple Blondies and Malted Milk Blondies.

For you chocoholics I’ve got lots of recipes for the blondies’ cousin: Fudgy Brownies, Sourdough Brownies, Habanero Brownies, Chocolate Cherry Brownies, Malted Milk Brownies, Roasted Beet Brownies, and White Chocolate Raspberry Brownies.

Since you’ve got your starter fed, peruse the entire list of My Best Sourdough Recipes. Have fun!

I know you hate to throw away that sourdough discard. Check out these recipes that use sourdough discard.

If you love this recipe as much as I do, I’d really appreciate a 5-star review.

a plate with three sourdough blondies

Sourdough Blondies

Yield: 24 blondies
Prep Time: 20 minutes
Bake Time: 30 minutes
Total Time: 50 minutes

Butterscotch blondies get a boost of flavor from sourdough discard. These blondies are both gooey and light at the same time.


  • 3 sticks (12 oz, 336g) unsalted butter, melted
  • 3 cups (24 oz, 672g) light brown sugar
  • 4 large eggs
  • 1 1/2 tablespoons vanilla extract
  • 1 cup (8 oz, 224g) sourdough discard (100% hydration)
  • 2 1/2 cups (12.5 oz, 350g) all purpose flour
  • 1/2 teaspoon table salt


  1. Preheat the oven to 375°F. Butter a 13" x 9" baking pan and line with parchment paper. You can just butter the pan but the parchment makes it much easier to remove the blondies from the pan.
  2. In a large bowl, combine the melted butter and brown sugar. Add the eggs and vanilla, stir until combined then vigorously stir for 30 seconds. Fold in the sourdough discard. Stir in the the flour and salt. Spread the batter into the pan.
  3. Bake until the center springs back when lightly pressed and a toothpick inserted in the center comes out with wet crumbs, about 30 minutes.
  4. Cool to room temperature before removing from the pan and cutting into 24 pieces.


I like to use a very ripe discard in this recipe, one that hasn't been fed for at least a week.

Did you make this recipe?

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Reinske Fokma

Monday 1st of March 2021

My second batch is now in the oven. The first batch, from a few weeks ago was incredibly nice. This time I am approaching it from a 'lockdown' perspective, and have used coconut cream (leftover from making curry) instead of butter; it smells amazing, even before going into the oven :)

Misty Bourlart

Saturday 10th of October 2020

I just whipped up a batch of these to use my first sourdough discard. My family loves them (and they're VERY hard to please.) The blondies were right in the sweet spot between being not sweet enough for my daughter or too sweet for my husband.

They turned out less dense than I expected and the lightness was greatly appreciated.

It's nice to know that I can make a pan of these anytime I have too much sourdough to deal with.

Kelley Reynolds

Tuesday 4th of August 2020

Oh, and I halved the recipe!


Friday 14th of August 2020

I also had this problem. They never got done. My discard was from a week ago and should have worked. The toothpick test came out clean. But they are basically raw. I baked them for 38 minutes to get to that point. I let them cool, cut into them, and found them to be oozing. So I put them back in for another 15 but it didn’t help. What are we missing here?

Kelley Reynolds

Tuesday 4th of August 2020

Hi, Thanks for sharing this recipe. Unlike one of your followers, mine turned out very gooey. Thought I was at the 30 minute mark, and did the toothpick as recommended. Oh well. Thanks for the vigorous egg to crust tip. Been waiting for that trick my entire baking life! I will make this again.


Thursday 2nd of July 2020

So how many times do we add the vanilla?

Eileen Gray

Thursday 2nd of July 2020

It's been fixed.