Sourdough Blondies

Since I am often thinking about, testing and perfecting new recipe ideas, I don’t always have time to re-visit old favorites. However, these sourdough blondies are one that my thoughts kept coming back to, and after perfecting the recipe I know they will be on a frequent rotation in my house. They are so quick to whip up and serve a crowd. Believe me when I tell you that these sourdough blondies (with freshly milled flour) are one of my very, very favorite sweet treats.

Why You’ll Love Sourdough Blondies

Whether you choose to make these sourdough blondies with freshly milled flour or good old all-purpose flour, you’re going to love this recipe. Sourdough blondies are made with vanilla extract and brown sugar, making them different from their brownie counterpart. They have a chewy texture and the most delicious flavor. You will love how easy this recipe is (with just a few simple ingredients) and that in no time you can whip up a delicious treat made with your sourdough discard.

Important Ingredients in Sourdough Blondies

  • All-Purpose or Freshly Milled Flour: I’m going to be honest with you, the all-purpose version is very good BUT the freshly milled version is the one I crave. I mill soft white wheat berries to get the fluffiest and most delicious flavor in these sourdough blondies. The whole wheat flour just works so well with the brown sugar, vanilla and toffee bits giving it a nutty and delicious flavor. If you can swing the freshly milled version – it’s worth it!
  • Brown Sugar: Blondies are traditionally made with brown sugar. This makes them chewy and gives a deep delicious flavor.
  • Egg: One egg is used in this recipe for rich flavor and texture.
  • Sourdough DiscardIn order to avoid a stronger sourdough flavor, use sourdough discard that is fresh or no more than a day or two old. I always use 100% hydration sourdough discard – discard that has been fed equal weights of flour and water. If your discard is very runny, you may need a little extra flour in this recipe.
  • Vanilla Extract: Blondies use a combination of brown sugar and vanilla extract to give them their sweet flavor. This may seem like a lot of vanilla extract, but it adds great flavor.
  • Unsalted Butter:  I use unsalted butter in all my baking recipes. You can control the flavor much better when you use unsalted butter. Salt content varies between brands of salted butter, and your baked goods may come out too salty when using salted butter. If you choose to use salted butter, decrease the salt a little bit in the recipe. Use melted butter for best results.
  • Baking Powder: This is the raising agent that is used in these bars.
  • Salt: Salt balances the flavors in these bars.
  • Toffee Bits and Chocolate Chips: I use the toffee baking bits I find at the grocery store for this recipe, they have become my favorite. I also add in semi-sweet chocolate chips. If you don’t like toffee or chocolate and want to substitute nuts, white chocolate chips or any favorite mix. you can. The total volume of mix-ins should be about 2 cups.

How to Make Sourdough Blondies

Mix Together Ingredients

Mix together melted, cooled butter with an egg and sourdough discard. Whisk until completely incorporated. There should be no stringy pieces of discard, just a smooth mixture before adding in the brown sugar and vanilla extract and mixing together. To a separate bowl fluff the flour with the baking powder and salt. Add the flour mixture on top of the sugar mixture and mix together. Mix in the toffee bits and semi-sweet chocolate chips.

Spread Batter Into Prepared Pan

Line a baking pan with parchment paper. Spread the blondie mixture evenly into the pan, nestling it into all the corners of the pan. Bake at 350ºF for about 30 minutes. The blondies will puff up, turn shiny and crack throughout the top when they are finished baking.

Bake and Cool

One of the most difficult parts of baking this sourdough blondie recipe is waiting for them to cool! Blondies really need that extra time to “set up” which happens during the cooling period. Don’t take them out of the pan until they have cooled for a couple of hours. Once cooled completely, remove them from the pan using the parchment paper and slice into pieces – I usually get 24 out of this pan. Enjoy!

Amy’s Recipe Tip

  • I prefer these sourdough blondies with soft white whole wheat flour. The combination of soft wheat and the brown sugar result in the most delicious flavor. I’ve also made these sourdough blondies with all-purpose flour and they were gobbled up quick – so if you don’t have the whole wheat flour, don’t worry. But if you can swing it – mill your own or purchase some for this recipe. Blondies on the left are made with whole wheat flour. Blondies on the right are made with all-purpose flour.


These sourdough blondies are amazing as is, but sometimes you want to switch things up a little.

  • If you want to make a smaller pan of these sourdough blondies – cut the recipe in half (just use an egg yolk) and bake in an 8 by 8 pan.
  • If you want a thicker blondie, cut the recipe into 3/4 (use a whole egg) and bake in an 8 by 8 pan. Add some extra time for baking so they bake all the way through.
  • You can substitute any mix-ins that you want in these blondies. I like toffee and chocolate chips, but you can add nuts, dried fruit, white chocolate chips – anything you’d like as long as the volume is about 2 cups worth.

How to Store Leftovers

Leftovers?! This does make a large pan of sourdough blondies, but we find that there are not usually too many, especially if we are bringing them to a gathering. But, when I make them at home for my family we often have leftovers. Slice them into squares, stick in an airtight container or ziplock bag and freeze for up to a couple months. When you’re ready to eat one, thaw and enjoy. And if you’re wondering if these taste good chilled – YES! I love them defrosted about 10 minutes from the freezer. Such a great treat!

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Frequently Asked Questions

I don’t have soft whole wheat flour. Can I use hard whole wheat?

You can, but hard whole wheat flour is going to have more protein than a soft wheat will which will make the blondies not quite as soft in texture. If you choose to use hard whole wheat, make sure to be careful when mixing the batter and don’t over-mix it to keep the blondies tender and soft.

I love toffee in these blondies. Can I leave out the chocolate chips?

Yes! I’ve done this a few times and love the flavor the extra toffee brings. If you do this, I would add about 1 1/2 cups of toffee bits or the equivalent of 1 bag of toffee bits (about 8 oz or 225 grams).

Sourdough Blondies

Chewy, gooey sourdough blondies are one of the most delicious treats. Sourdough blondies are made with simple ingredients and yummy mix-ins, toffee and chocolate chips in this recipe. With sourdough discard and freshly milled flour (if you have it), everyone will be asking for more. Enjoy!
5 from 7 votes
Prep Time 20 minutes
Cook Time 30 minutes
Total Time 50 minutes
Course Dessert
Cuisine American
Servings 1 9 by 13 pan


  • 170 grams unsalted butter melted and cooled, 12 Tablespoons
  • 1 large egg about 50 grams
  • 100 grams sourdough discard about 1/2 cup, see recipe notes
  • 340 grams brown sugar about 1.5 cups
  • 15 grams vanilla extract about 1 Tablespoon
  • 245 grams all-purpose or freshly milled soft white wheat flour about 1 3/4 cups, see recipe notes
  • 5 grams baking powder about 1 teaspoon
  • 5 grams salt about 3/4 teaspoon
  • 150 grams toffee bits about 3/4 cup, see recipe notes
  • 180 grams semi-sweet chocolate chips about 1 cup, see recipe notes


  • Preheat the oven to 350ºF and prepare a 9 by 13 pan with parchment paper. Let the parchment paper come up over the edges so you can easily pull the blondies out of the pan when they have cooled. Find instructions for lining a pan with parchment here.
  • To a medium-sized bowl, whisk together melted butter, egg and sourdough discard until completely incorporated and smooth. Add the brown sugar and mix with a wooden spoon or spatula. Stir in the vanilla extract.
  • To a small bowl add the flour (freshly milled if you can!), baking powder and salt. Fluff with a fork.
  • Pour the flour mixture on top of the sugar mixture and stir until mostly combined. Add the toffee bits and chocolate chips. Stir until combined.
  • Spread the batter evenly into the pan and bake for 30 minutes at 350ºF. Blondies will puff up in the oven and the top will look shiny and cracked. Let blondies cool for an hour or two before removing from the pan. They will sink back down as they are cooling, resulting in the chewy blondie texture and taste. Enjoy!


Sourdough DiscardIn order to avoid a stronger sourdough flavor, use sourdough discard that is fresh or no more than a day or two old. I always use 100% hydration sourdough discard. This means that your starter is fed equal weights of flour and water. If your discard is very runny, you may need a little extra flour in this recipe. 
Freshly Milled Flour: These sourdough blondies are very good with all-purpose flour. But they are incredible with freshly milled soft white wheat flour. I buy the Frederick wheat berries from Janie’s Mill and mill them in my Harvest Grain Mill.
Mix-Ins: I like a combination of toffee bits and chocolate chips in these blondies, but you can use any mix-ins that you want. Nuts, white chocolate – anything you like. The total volume of mix-ins should be about 2 cups for this recipe.
Keyword easy sourdough discard recipe, freshly milled blondies, freshly milled dessert, sourdough blondies, sourdough discard blondies, sweet sourdough blondies
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Recipe Rating


    1. It is 1.5 cups. I changed it a few days ago but maybe need to clear the cache so it shows up correctly. Thanks for letting me know.

  1. 5 stars
    Just made these. I wanted a longer ferment of the flour, so I mixed the starter with the butter, added the flour & let it ferment overnight on the counter. Mixed the brown sugar with the egg, added vanilla, the fermented dough mixture, & the rest of the ingredients. OMG, these are the best blondies we’ve ever had. Amy ur the bomb!

  2. 5 stars
    I’ve made these twice and they are a hit with my family! I omit the toffee bc I never bought it and it’s still super delicious.