Sourdough Discard Brown Butter Valentine Blondies

If you've got kids, you already know that anything sweet is a win. But something sweet and a little colorful with a theme? That's a whole different level of excitement. These Sourdough Discard Brown Butter Valentine Blondies are exactly that. They're fun, they're festive, and they give you the perfect excuse to use up that sourdough discard sitting in your fridge.

Honestly, these blondies are dangerously good. We're talking chewy centers, crackly tops, and that brown butter depth that takes a regular blondie and turns it into something you genuinely can't stop eating. The sourdough discard adds this subtle tang and gives these blondies an almost caramel-like complexity that you just don't get from a standard recipe.

No mixer needed here. Just a whisk, a spatula, and about 30 minutes of your time. Let's get into it.

Why These Blondies Work So Well

Let me break down what makes these so special:

Brown Butter — This is the move. Browning your butter gives you these toasty, nutty, caramel-like notes that you just can't replicate with regular melted butter. It's an extra five minutes that completely transforms the flavor.

Sourdough Discard — This gives your blondies moisture and depth without a big sour punch. You get just enough tang to add complexity, and it keeps everything incredibly fudgy. My discard is normally pretty thick, and that's going to give you an even fudgier blondie. If your discard is more on the watery side, you'll just end up with a slightly looser batter (still delicious, just a little different texture).

No Mixer Required — A hand whisk and a spatula are all you need.

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Ingredients

Wet Ingredients

• ½ cup unsalted butter (115g)
• 1 cup brown sugar (200g)
• 1 large egg (50g)
• 1 large egg yolk (18g)
• ½ cup sourdough discard (120g)
• 1 teaspoon vanilla extract (5g)

Dry Ingredients

• 1 cup + 2 tablespoons all-purpose flour (156g)
• ½ teaspoon salt (3g)
• ½ teaspoon baking powder (2g)

Pink Swirl Batter

• ¾ cup reserved blondie batter (180g)
• 6–8 drops Watkins natural pink/red food coloring
• 1 tsp of flour

Equipment

• Small saucepan
• Hand whisk
• Spatula
• 8×8 inch baking pan
• Parchment paper
• Skewer or knife (for swirling)
• 2 mixing bowls

Instructions

Step 1: Brown the Butter

Melt the butter in a small saucepan over medium heat. Cook, stirring continuously, until it turns golden and you see nutty brown flakes forming at the bottom. It's going to start foaming and that's exactly what you want. Once it's golden and fragrant, remove it from the heat quickly and let it cool for about 5 minutes.

Step 2: Mix the Wet Ingredients

Whisk together the brown butter and brown sugar until smooth. About one minute with a hand whisk should do it, the sugar should turn a slightly lighter color after your minute is up. Then whisk in your egg, egg yolk, sourdough discard, and vanilla until everything is well combined.

Step 3: Combine the Dry Ingredients

In a separate bowl, mix together your flour, salt, and baking powder.

Step 4: Bring It All Together

Fold the dry ingredients gently into the wet mixture until just combined. The key is to not overmix here. You want to stop as soon as you don't see any dry flour streaks. Overmixing is going to make them dense and tough, and we want fudgy.

Step 5: Prepare the Pink Swirl

Remove ¾ cup (180g) of batter into a small bowl. Add 6 drops of Watkins natural pink/red food coloring and mix well. If the color looks too light, add a couple more drops until you're happy with it. Check the thickness at this point. You want the pink batter to be slightly thicker than the main batter. I typically add 1 teaspoon of flour to the pink batter to get that right consistency.

Because I use natural, no-artificial-dye food coloring, the red swirl is more muted and rustic than a traditional bright red. Natural colorings (like plant-based or juice-derived blends) tend to soften in the oven and can shift slightly in shade once mixed into batter. If you’d like a deeper, more dramatic red, you can add an extra drop or two of coloring, stir a tiny pinch of beet powder into the swirl, or use a small touch of gel food coloring for a more vibrant finish. I personally don’t mind the moodier look. Especially when it means I can’t avoid artificial dyes.

Step 6: Assemble and Swirl

In a greased and parchment paper-lined 8×8 pan, spread the plain blondie batter evenly across the bottom. Dollop the pink batter on top in spoonfuls. I did about 1/2 tbsp doolops and looking back I think 1 tsp dollops would have worked better. Using a skewer or knife, gently swirl in figure eights or heart shapes. Three to four passes max. Don't over-swirl or you'll end up with a muddy mess instead of those beautiful defined swirls.

Step 7: Bake

Bake at 350°F (175°C) for 22–26 minutes. The center is going to look slightly underdone, and that's exactly what we want. It'll set as it cools. Let them cool completely in the pan before cutting. I had a heart shaped cookie cutter that I used to make these extra valentines ready.

Tips for the Best Blondies

• Room temp eggs — Pull them out of the fridge ahead of time. This helps everything incorporate more smoothly.
• Don't overmix — I can't say this enough. Overmixing develops gluten, which makes your blondies dense and tough instead of chewy and fudgy.
• The center should jiggle slightly — If the center still has a little wobble when you pull them out, you're right where you want to be. We want to slightly underbake these — that's what makes them fudgy instead of dry.
• Cool completely — I know it's hard but letting them cool all the way gives them time to set and makes for cleaner cuts.

A Note on Sourdough Discard

My discard is normally pretty thick, and that's going to give you the fudgiest blondie. If your discard is more on the watery side, your batter will be a little looser. Which is totally fine, the blondies will still be amazing. The tang from the sourdough really does give these so much depth and this caramel-like complexity that you just won't get from a regular blondie recipe. It's one of those ingredients that makes people say, "What's in these?" and they never guess sourdough.

These are such a fun Valentine's treat. My kids go absolutely crazy for them, and honestly, I can't blame them. You get that rich, toasty brown butter flavor, the subtle tang from the discard, a chewy fudgy center, and those gorgeous pink swirls that make them feel so festive. And you finally get to use that sourdough discard you've had sitting around.

Happy Valentine's Day, friends. Go make these.