Key Lime and White Chocolate Sourdough Blondies

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As summertime comes into full swing, I really enjoy baking with seasonal produce. I love using citrus in baked goods to really brighten a dish. One of the best ways to use citrus in the summer is with key limes. Today I am sharing another gem to add to your collection of sourdough discard recipes. These key lime and white chocolate sourdough blondies combine a classic blondie base with tangy limes and rich white chocolate for the ultimate dessert bar. It’s reminiscent of key lime pie in handheld form. The addition of sourdough discard is also a plus for avoiding waste in the kitchen. 

If you enjoy this recipe and want to try other blondie variations, I recommend you check out my recipe for white chocolate cranberry sourdough blondies. They can be made with a cream cheese frosting as well to copycat Starbucks’ cranberry bliss bars!

Ingredients & Substitutions: 

For the sourdough blondie batter:

• All-purpose flour: I’ve also used bread flour in this recipe, and it came out just fine. Bread flour has a higher proportion of gluten than all-purpose flour.  
• Baking powder
• Salt: Omit this if you use salted butter.
• Unsalted butter: You can use salted butter if that’s all you have. Just omit the salt.  You’ll melt and brown the butter on the stove first and allow it to cool before adding to the rest of the wet ingredients. Browning the butter is a must for the perfect gooey blondie. When you brown butter, the milk solids caramelize, which adds a rich and nutty flavor to your baked goods. 
• Brown sugar: You can use dark brown sugar or light brown sugar in this recipe. Brown sugar gets its rich, warm color from the addition of molasses. Molasses is a thick syrup produced as a byproduct from refining sugarcane. The darker the brown sugar, the higher the molasses content. If you’ve ever tried straight molasses, you know it’s pretty poignant. In small doses, it adds a lovely caramel or toffee-like flavor that I just love in baked goods and desserts. 
• Sourdough discard: For this recipe, you’ll be using unfed sourdough starter, aka sourdough discard. This is the portion that gets removed from the jar every time you feed your starter. Unlike in sourdough bread, these bars utilize baking powder as the leavening agent. The unfed sourdough discard doesn’t add any additional leavening to the recipe.
• Eggs
• Pure vanilla extract
• Lime zest: I used key limes in this recipe. They are in season from mid-June to September. Key limes have a subtle, yet distinct flavor and aroma that sets them apart from regular, or Persian, limes. They are known for being slightly more tart and less acidic than regular limes. They also have a stronger, more aromatic scent. You can use regular limes in this recipe. However, if you have access to key limes, I recommend that you give them a try. 
• White chocolate chips: I used Ghirardelli white chocolate chips in this recipe. I prefer real white chocolate chips because they contain quality ingredients like cocoa butter. You can also substitute a roughly chopped bar of white chocolate in place of the chocolate chips.  However, in a pinch, you can use white “morsels.” They have a similar taste to white chocolate, but often contain stabilizers and gums, and often don’t contain any cocoa butter. When in doubt, read the ingredient list, as this often varies by brand and manufacturer. 

For the topping: 

You can eat these sourdough discard blondies as is, or you can drizzle or dip them in white chocolate. You can also use the following recipe for a cream cheese frosting. 

• Cream cheese:  You can also substitute Neufchatel. It has a very similar taste to cream cheese, but is slightly tangier. Compared to cream cheese, Neufchatel has a lower fat content and higher moisture content. It works well in recipes that call for cream cheese, such as frostings, dips, or spreads. You can typically find it in the same section as regular cream cheese. 
• Powdered sugar
• Lime juice
• Lime zest
• White chocolate: melted and folded into the frosting. You can also melt additional white chocolate for drizzling on top of the bars. This isn’t entirely necessary, but adds a nice aesthetic touch. 

How to make Key Lime and White Chocolate Sourdough Blondies  

Preheat your oven to 350° F. Line a 9×13 inch baking pan with parchment paper. Spray the paper with oil or grease with butter and set aside. 

In a stainless steel or other light-colored saucepan, melt the butter over medium heat. The butter will form bubbles and foam, so you’ll need to push it aside with a spoon in order to watch the color of your melted butter. Once the milk solids have turned a golden brown color, remove from heat. As it gets darker, don’t step away, as it can quickly burn. (I speak from experience, haha!) Pour the butter into a separate bowl and set aside to cool. 

In a large bowl or stand mixer, combine the cooled, melted butter with brown sugar. Add the sourdough discard, eggs, vanilla extract, and zested lime and stir to combine. 

To make it easier (and less dishes) I add the dry ingredients to the same mixing bowl after the wet ingredients are combined. Alternatively, in a separate medium bowl, whisk together the all-purpose flour, baking powder, and salt. You can then add the dry ingredients to the wet and stir to combine. Make sure to scrape down the sides and bottom of the bowl to ensure everything is incorporated. 

Fold in the white chocolate chips.

Spread the batter evenly into the prepared baking pan using a rubber spatula. Bake for 22-25 minutes, or until the top of the bars are shiny and lightly golden brown. They may even appear slightly underbaked in the center. This is fine and will yield a deliciously chewy and moist texture when cool. Remove from the oven and allow to cool on a wire rack. 

Once the blondies are cool to room temperature, you can prepare the frosting. I usually make my blondie base in the morning or night before, and then frost at least 3 hours later so the chocolate and frosting doesn’t melt off the bars. 

Start by melting the white chocolate in a small bowl. You can do this in the microwave and set aside. 

In a medium bowl, mix together the cream cheese, powdered sugar, vanilla extract, and orange zest. Gradually add the white chocolate, mixing until smooth.

Spread the frosting evenly over the cooled blondies. 

If desired, drizzle with the melted white chocolate. 

Cut the blondies into squares or triangles and serve. 

Storage:

Without the frosting, these key lime and white chocolate sourdough blondies can be stored at room temperature in an airtight container for about 1 week. However, they start to get dryer as time goes by. If frosted, you’ll definitely want to keep these in an airtight container in the fridge. They will last slightly longer in the fridge, but they’ve never lasted in my house beyond about a week. You can also freeze these bars. I recommend wrapping in seran or plastic wrap and then storing in an airtight container for up to 3 months. To thaw, simply pull out of the freezer and allow to come to room temperature before serving. 

Pairing suggestions: 

• In the summer, I recommend pairing these blondie bars with a cool glass of iced tea or iced coffee. 
• If you’re making these blondie bars in the cooler months, try pairing with a latte or just a simple cup of black coffee or tea.

These delicious key lime and white chocolate sourdough blondies are perfect for holiday parties, office gatherings, or just a cozy afternoon with a loved one. And the best part? They’re made with sourdough discard, so you’re not only creating a tasty treat, but also reducing food waste. It’s a win-win! Whether you’re a seasoned baker or just looking for a fun way to use up your sourdough discard, this recipe is sure to satisfy your sweet tooth. 

I hope you enjoy! Cheers! 

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