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creamy custard swirl blondies

Creamy Custard Swirl Chocolate Chip Blondies

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Prep Time 20 minutes
Cook Time 28 minutes
Resting Time 30 minutes
Total Time 1 hour 18 minutes
Course Dessert
Cuisine American
Servings 16 squares

Equipment

  • 1 8x8-inch baking pan
  • 2 Mixing bowl
  • 1 Medium saucepan
  • 1 Whisk
  • 1 Rubber spatula
  • 1 hand mixer or stand mixer
  • 1 measuring cup set
  • 1 measuring spoon set
  • 1 parchment paper sheet
  • 1 Wire rack
  • 1 toothpick

Ingredients
  

  • 6 tablespoon unsalted butter melted and slightly cooled
  • 1/2 cup light brown sugar packed
  • 1/4 cup granulated sugar
  • 1 large egg room temperature
  • 2 teaspoon vanilla extract divided
  • 1 cup all-purpose flour spooned and leveled
  • 1/2 teaspoon baking powder
  • 1/4 teaspoon fine sea salt
  • 3/4 cup semi-sweet chocolate chips
  • 3 tablespoon unsalted butter for custard
  • 1 cup whole milk
  • 2 large egg yolk
  • 3 tablespoon granulated sugar for custard
  • 1 tablespoon cornstarch
  • 1/8 teaspoon fine sea salt for custard

Instructions
 

  • Line an 8x8-inch pan with parchment paper with overhang and lightly grease.
  • In a bowl whisk the melted butter, brown sugar, and granulated sugar until glossy and combined.
  • Whisk in the whole egg and 1 teaspoon vanilla until smooth.
  • In a separate bowl whisk the flour, baking powder, and 1/4 teaspoon salt.
  • Fold the dry ingredients into the wet just until no dry streaks remain.
  • Fold in the chocolate chips and set the blondie batter aside.
  • For the custard, heat milk in a saucepan over medium until steaming but not boiling.
  • In a bowl whisk egg yolks, 3 tablespoons sugar, cornstarch, and 1/8 teaspoon salt until silky.
  • Slowly whisk the hot milk into the yolk mixture to temper, then return to the saucepan.
  • Cook over medium, whisking constantly, until thick bubbles appear and custard coats the whisk, 1 to 2 minutes.
  • Off heat whisk in 3 tablespoons butter and 1 teaspoon vanilla until smooth.
  • Spread two-thirds of the blondie batter evenly in the prepared pan.
  • Dollop warm custard over the batter in 6 to 8 spoonfuls.
  • Spoon the remaining blondie batter in between the custard dollops.
  • Use a butter knife to gently swirl the batter and custard together without overmixing.
  • Bake at 350°F (175°C) for 26 to 30 minutes until the edges are set and a toothpick in a non-custard area comes out with moist crumbs.
  • Cool the pan on a wire rack for 30 minutes, then lift blondies out using parchment and cool completely before slicing.
  • Cut into 16 squares and serve slightly warm or at room temperature.

Notes

For the cleanest swirl, keep the custard slightly warm and spoonable rather than hot or fully cooled, and avoid dragging the knife too deeply to prevent the custard from sinking. Do not overbake; the custard pockets will remain softer than the blondie crumb, so check doneness in the batter zones only. If the batter feels thick, reserve a tablespoon of milk to loosen it just enough to dollop. Chilling the cooled slab for 30 minutes makes tidy cuts, and you can warm slices for 10 to 15 seconds to restore gooey texture. Add toasted pecans or a pinch of cinnamon for variation, and store covered in the fridge up to 4 days or freeze well-wrapped for 2 months.
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