Preheat the oven to 350°F. Line an 8x8-inch baking pan with parchment paper, leaving overhang on the sides for easy removal.
In a large bowl, stir together the melted butter and brown sugar until well combined.
¾ cup unsalted butter, 1¼ cups brown sugar
Add the vanilla extract and egg and mix until smooth.
2 teaspoons vanilla extract, 1 large egg
Sift in the flour, cornstarch, baking powder, and salt. Stir just until combined.
1½ cups all-purpose flour, 1 teaspoon cornstarch, ½ teaspoon baking powder, ½ teaspoon salt
Fold in the white chocolate chunks, then gently fold in the raspberries.
1 cup white chocolate, ½ cup fresh raspberries
Spread the batter evenly into the prepared pan and smooth the top.
Bake for 25-30 minutes, until the edges are golden and a toothpick inserted in the center comes out mostly clean.
Let the blondies cool completely in the pan on a wire rack.
Lift out using the parchment paper, cut into squares, and serve.
Notes
🥡 STORAGE: Store in an airtight container at room temperature for up to 3 days.Refrigerate for up to 5 days for longer freshness.♨️ REHEATING: Microwave individual blondies for 10-15 seconds.Warm in a 300°F oven for 5-7 minutes if reheating multiple pieces.❄️ FREEZING: Freeze cut blondies in a single layer, then transfer to a freezer-safe container.Freeze for up to 2 months.Thaw at room temperature before serving.💡 TIPS FOR BEST RESULTS: Use fresh raspberries when possible for less moisture.Do not overmix the batter to keep blondies tender.Allow full cooling before slicing for clean cuts.🍳 ALTERNATE COOKING METHODS: Double the recipe and bake in a 9x13-inch pan, adding 5-10 minutes to bake time.Line the pan well to prevent sticking, especially with juicy berries.♻️ LEFTOVERS: Chop and use as a topping for ice cream or yogurt.Crumble over parfaits or milkshakes.📝 NOTES: Blondies will firm up as they cool.Slight moisture in the center is normal and keeps them soft.