Blueberry Walnut Blondie Bars

Blondies are a relatively recent discovery for me, but once I tried them, there was no going back. I especially love them with fruit, and the flavors in these blueberry walnut blondie bars are simply superb. The juicy blueberries, buttery walnuts, and chewy cookie bar edges make these a must-try dessert bar!

These blueberry blondies are especially perfect for late spring and summer (when blueberries are in season here in the U.S.), but you can usually find ripe blueberries year-round. Which is fortunate, because you definitely shouldn’t wait to try these delicious bars! 😉

blueberry walnut blondie bars

Walnut Bars with Blueberries

The first blondie recipe on my blog, these raspberry almond blondies, was an instant favorite of mine (and my husband). They’re so full of bright berry and luxurious almond flavor, not to mention the out-of-this-world texture. But I may have quite possibly outdone myself with this blueberry walnut version!

These blondies taste like a cross between a blueberry muffin and sugar cookie, with moist centers and chewy edges. The walnuts get all toasty and add a delicious hint of nutty flavor.

I love how easy these are, too. There’s no electric mixer needed – just a good old-fashioned whisk and mixing bowl!

What’s a blondie?

A blondie is similar to a brownie, but without the chocolate – kind of like a cookie bar, but more cakey in the middle. On its own, it has a buttery vanilla flavor, so it lends itself to tons of tasty flavor variations!

I use brown sugar in my blondies for a light caramel flavor, too. Plus, it yields a more fudgy texture, which is definitely what we’re after here!

(If you’re looking for a brownie recipe, these peanut butter banana brownies are delish!)

Recipe Ingredients

Here’s what you’ll need to make these blueberry walnut bars:

  • flour: All-purpose flour gives us a soft and chewy texture.
  • butter: Melted butter helps bind the ingredients, enhances the flavor, and makes the bars deliciously moist.
  • brown sugar: I prefer brown sugar over white sugar in blondies, for a hint of caramel flavor and a fudgy texture. You can substitute white sugar if needed, though.
  • eggs: We’re using one egg and one egg yolk to give the bars rise and structure. Using the egg yolk (in addition to one full egg) is important for the right texture.
  • vanilla extract: For that essential rich vanilla flavor.
  • baking powder: To give the bars rise and structure.
  • blueberries: For sweet and juicy bursts of flavor! Their sweetness pairs perfectly with the buttery, toasty walnuts.
  • walnuts: These add crunch and a nutty flavor. They’re a delicious match for the blueberries, but you can use almonds or pecans instead if you’d like!
  • salt: For flavor enhancement and balance.

Have leftover blueberries? Try these baked blueberry glazed donuts or these blueberry white chocolate muffins!

blueberry blondies with walnuts and a glass of milk in the background

How to Make Blueberry Walnut Blondie Bars

You’ll need an 8×8 inch square baking pan for these. (Or, you can make a double batch in a 9×13 inch pan, but the baking times may vary). Grease or spray the pan with cooking spray, then line it with parchment paper, making sure the paper sticks to the sides of the pan.

Next, make the batter! Melt butter in the microwave, then combine it with the brown sugar in a mixing bowl. Whisk vigorously for a minute (this helps create that lovely, crackly top!).

Once the mixture is cooled to room temperature, add in vanilla extract, egg, and egg yolk. Whisk vigorously again until smooth.

In a separate bowl, combine the dry ingredients (flour, baking powder, and salt). Gently stir the dry ingredients into the wet ingredients with a spatula. (I recommend sifting in the dry ingredients to prevent lumps). Stir until it’s mostly combined – we’ll finish stirring in the next step.

Very carefully fold in the blueberries and walnuts (you don’t want the blueberries to burst, or you’ll get purple batter). The batter should no longer have any flour streaks at this point.

Use the spatula to scoop the batter into your lined baking pan. Smooth it out on top, then sprinkle on additional blueberries and walnuts if desired.

Bake at 350 degrees Fahrenheit, until a toothpick inserted into the center comes out with just a few crumbs, and the edges and top are golden brown. (See detailed baking times in the recipe card at the end of this post.)

stack of blueberry walnut bars with a glass of milk

Blondie Baking Tips

A few tips to make sure your blondie bars turn out perfect:

  • Grease the baking pan before adding the parchment paper (so it sticks better)
  • Use room-temperature eggs (set them out on the counter ahead of time)
  • Be sure to whisk the hot melted butter and brown sugar vigorously to get that crackly top
  • Make sure the butter/sugar mixture has cooled somewhat before adding the eggs
  • Be gentle when folding in the blueberries
  • When smoothing out your batter in the pan, make sure it reaches all the way to the edges and corners

How to Slice Blondies

First, let the bars cool completely. Using the parchment paper, lift the blondies from the pan. Run a large knife under hot water, then wipe it dry and use it to slice the blondies.

For easier/cleaner slicing, transfer the blondies to the fridge – once they’re fully cooled – and let them chill for 20-30 more minutes before slicing.

blueberry walnut blondie bars on parchment paper

Storage Tips for Blueberry Walnut Bars

Once they’re fully cooled, store these in an airtight container at room temperature for up to 3 days, or in the fridge for up to 5 days. The flavor and texture may be better if stored at room temp.

One caveat: for the absolute best chewy texture and crispy edges, these are best enjoyed the same day they’re made, if possible. But don’t worry, they’ll still taste delicious even after a few days!

You might also enjoy these almond butter cookie bars or these pecan sweet potato bars!

Can I use frozen blueberries?

Frozen blueberries should work here, but I recommend thawing them first and drying them very well with a paper towel. Otherwise, they may give off too much moisture when baked.

Recipe Variations & Toppings

Want to try something a little different? Here are some ways to switch up this recipe:

  • Top the bars with a drizzle of melted white chocolate or powdered sugar/icing
  • Add shredded coconut to the batter or on top
  • Use pecans or almonds instead of walnuts
  • Add lemon zest
  • Add chocolate chips (any kind!)
blueberry walnut blondies on parchment paper

I’m suddenly inspired to go blueberry picking…probably so I have an excuse to make these again! 🙂

If you make these blueberry walnut blondie bars, I’d love if you shared your thoughts with a rating and comment below.

More dessert recipes with fruit:

Blueberry Walnut Blondie Bars

These blueberry walnut blondie bars are simply superb. The juicy blueberries, buttery walnuts, moist texture, and chewy edges make these a must-try dessert bar!
Prep Time 15 mins
Cook Time 30 mins
Total Time 45 mins
Course Dessert
Cuisine American
Servings 9 bars

Ingredients
  

  • 8 Tbsp unsalted butter (1 stick)
  • 1 cup brown sugar (packed)
  • 1 large egg (at room temperature)
  • 1 egg yolk (at room temperature, see notes for tips)
  • 1 tsp vanilla extract
  • cup all-purpose flour (spooned and leveled with a knife)
  • ½ tsp baking powder
  • ½ tsp salt
  • 1 cup blueberries (about 8 oz, plus extra for topping)
  • ½ cup walnuts, chopped (plus extra for topping)

Instructions
 

  • Preheat oven to 350°F (176°C). Spray or grease an 8x8in square pan (metal nonstick or glass). Line with parchment paper. (Greasing the pan first helps it stick better). Set aside.
  • In a bowl, combine flour, baking powder, and salt. Mix with a whisk and set aside.
  • In a separate bowl, melt butter in the microwave in 30 second intervals at 50% power. Combine melted butter and brown sugar in a large mixing bowl and whisk vigorously for one minute.
  • Add egg, egg yolk, and vanilla extract. Whisk vigorously until fully incorporated.
  • With a spatula, add dry ingredients to wet ingredients. (Using a sifter is best to avoid clumps.) Gently stir until almost fully mixed. Avoid over-mixing.
  • Carefully fold in the blueberries and walnuts. (The batter should no longer have any flour streaks at this point.)
  • Use the spatula to scoop the batter into your lined baking pan. Smooth out on top. Lightly press additional blueberries into the top of the batter and sprinkle on additional chopped walnuts, if desired.
  • Bake for 25-30 minutes if using a metal nonstick pan, or 35-40 minutes if using a glass pan. The blondies are done when a toothpick inserted into the center comes out with just a few crumbs (it should still be somewhat moist), and the edges are golden brown and starting to pull away from the pan.
  • Let cool completely. Once cool, use the parchment paper to lift the blondies from the pan. Slice with a large knife.**

Notes

*How to Separate an Egg Yolk: gently crack an egg on the rim of a bowl, as close to the center of the shell as possible. Pull the egg shell halves apart over the bowl, letting the yolk settle in one half. Let the egg whites run over the edge of the egg shell half. Then, carefully transfer the yolk into the other shell half, letting more egg whites run off. Repeat until most of the egg white is gone and just the yolk remains.
**For easier/cleaner slicing, transfer the blondies to the fridge (after they’re completely cooled) to chill for 30 minutes before slicing.
Storage Tips: Once the blondies are fully cooled, store them in an airtight container at room temperature for up to 3 days, or in the fridge for up to 5 days.
To use frozen blueberries: be sure to completely thaw them first and dry them very well with a paper towel. Otherwise, they may give off too much moisture when baked.
Keyword bars, blondies, blueberries, fruit, walnuts

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