Step 1

Make the blondies: Preheat the oven to 250°F (120°C).

Step 2

Spread the white chocolate in a single layer in a large glass baking dish. Bake, stirring with a rubber spatula every 10 minutes, until the chocolate is caramelized, 30-40 minutes total. Remove the chocolate from the oven and let sit while you make the brown butter.

Step 3

Increase the oven temperature to 350°F (180°C). Line a 9 x 13 x 2-inch baking pan with 2 sheets of aluminum foil, leaving a bit of overhang around all of the edges. Grease the foil lightly with nonstick spray.

Step 4

Melt the butter in a medium saucepan over medium heat. Bring to a boil, stirring frequently with a heat-safe rubber spatula. As the water begins to boil out of the butter, the milk solids in the butter will separate, sink to the bottom of the pot, and begin to toast. Stir constantly until the butter turns nutty brown, about 10 minutes total. Turn off the heat, add the caramelized chocolate, and stir to melt and combine with the browned butter. Let cool slightly, about 5 minutes.

Step 5

In a large glass bowl, whisk together the brown sugar, granulated sugar, maple syrup, malted milk powder, kosher salt, eggs, vanilla, and maple extract until smooth and homogenous. Slowly stream in the white chocolate mixture and continue whisking until combined. Sift in the flour and stir with a rubber spatula to bring the batter together.

Step 6

Pour the batter into the prepared pan and smooth the top.

Step 7

Bake the blondies until golden brown and set, 35–40 minutes. Remove from the oven and let cool for 1 hour.

Step 8

Make the maple caramel: In a small, heavy-bottomed pot fitted with a candy thermometer, heat the maple syrup over medium heat until the temperature reaches 225°F (107°C). Remove the pot from the heat and add the butter. Swirl the pan until the butter melts completely, then slowly pour in the heavy cream and sprinkle in the flaky sea salt. Use a heat-safe spatula to stir until just combined. Let the caramel cool until thickened slightly, about 15 minutes.

Step 9

Make the ganache: Fill a small pot with 1 inch of water and bring to a boil over medium-high heat. Add the white chocolate to a medium glass bowl and set over the boiling water, making sure the water is not touching the bottom of the bowl. Pour in the heavy cream and stir with a small rubber spatula until completely melted and smooth, about 5 minutes.

Step 10

Lift the blondies from the pan, remove and discard the foil, and place the blondies on a wire rack set over a baking sheet. Pour the ganache over the blondies and use an offset spatula to cover completely. Sprinkle the flaky sea salt on top, then use a spoon to drizzle the caramel over the ganache to create a marbled effect.

Step 11

Slice into 12 pieces.

Step 12

Enjoy!