These brown butter mixed berry blondies are packed with layers of flavor. The brown butter brings a deep, nutty richness, while swirls of strawberry, raspberry, and blueberry jam add brightness and just the right amount of contrast. Plus the pockets of white chocolate melt into the bars, rounding everything out with a creamy sweetness. It’s an easy treat, especially perfect for using up those extra jars of jam sitting in your pantry! If you like fruit blondies, you will enjoy my Brown Butter Peach Blondies or if you like mixed berries this Olive Oil Mixed Berry Cake is delightful!
The base of the recipe. Browning it creates deep, nutty flavor and those signature brown specks.
Boosts the browning process and intensifies the caramelized flavor.
Adds moisture and chewiness while contributing subtle molasses notes.
Balances texture and helps create slightly crisp edges.
The extra yolk adds richness and keeps the blondies dense and fudgy, not cakey.
Enhances both the butter and berry flavors.
Balances sweetness and sharpens flavor.
Softens the crumb and keeps the blondies tender and thick.
Provides structure without making the blondies dry.
Creates a glossy, jammy top layer and adds acidity to balance the richness.
Add creamy sweetness and texture contrast.
Use thick, high-quality jam or preserves. Do NOT jelly as they are too runny and watery and won't hold their texture in these blondies.
In a small saucepan over medium heat, melt butter. Continue cooking until golden brown flecks form and it smells nutty. Transfer to a large bowl, mix in milk powder if using and cool for 10–15 minutes.
Preheat oven to 350°F. Line an 8x8 baking pan with parchment paper.
Whisk brown sugar and granulated sugar into the warm brown butter. Add egg, egg yolk, and vanilla. Mix until smooth and glossy.
Fold in flour, cornstarch, and salt until just combined. Do not overmix. Mix in white chocolate till combined.
Spread batter evenly into prepared pan. Dollop jam across the top and gently swirl using a butter knife, but don't go too far into the batter.
Bake for 25–30 minutes, until the edges are set and lightly golden. A toothpick inserted at the base, not touching the jam shows moist crumbs and no raw batter. Also, the top of the jam is glossy but not liquidy. Let blondies cool in the pan for at least an hour to further set.
Why are my blondies cakey instead of fudgy?
Too much flour or over baking will make them cakey. Measure flour carefully and slightly underbake.
Can I use fresh berries instead of jam?
Not recommended. Fresh berries release too much moisture and can make the blondies soggy. But you can use homemade jam.
Can I skip the white chocolate?
Yes. The blondies will be less sweet and more berry-forward.
Why brown the butter?
Brown butter adds depth and richness that regular melted butter cannot replicate.
How do I get clean slices?
Cool completely, then chill in the fridge for at 30 minutes before slicing.
You want golden, not burnt. Think toasted hazelnut, not coffee ash.
Measuring flour properly makes a big difference in how baked goods turn out. For best results, use a kitchen scale and measure in grams. This ensures consistency and prevents adding too much flour, which can make the cake dry.
If you don’t have a scale:
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