Prepare the pan: Line an 8-inch by 8-inch square baking pan with parchment. Preheat the oven to 350℉ / 177℃.
Prepare the mixing bowl: In a medium bowl, mix 1 cup dark brown sugar, ½ teaspoon ground cardamom, and 2 tablespoons malted milk powder together.
Brown the butter: In a small saucepan, melt 1 stick unsalted butter over medium heat. Stirring frequently, continue cooking butter as it begins to foam up considerably. Once the foam subsides, the butter should smell nutty and toasty (and appear light brown in color). Immediately remove the butter from the heat, then stir into the brown sugar-cardamom mixture.
Add the rest of the wet ingredients: Check to make sure the batter is lukewarm (if hotter, the egg may curdle, so let it cool if needed), whisk in 1 large egg and 1 teaspoon vanilla extract. Whisk for about 1 minute until mixture lightens in color and becomes thick and ribbony.
Add the dry ingredients: Gently fold in ½ teaspoon sea salt and ⅞ cup all-purpose flour until just combined. Fold in ⅔ cup toasted nuts (chopped) and ½ cup white chocolate (chopped).
Bake: Pour the batter into your parchment-lined baking pan and sprinkle with flaky salt. Bake for 15-25 minutes (depending on the size of your baking pan) until the blondies feel set, the top is crackly and doesn't wiggle and the sides are golden brown. The blondies will still feel slightly soft (if they feel firm, they are overdone). Once done, remove from the oven and let cool for 5 minutes. Gently lift up the blondies in the parchment paper and set on a wire rack to cool, about 15-20 minutes.
Cut into squares and serve, or, if desired, you can place the blondies (uncut and uncovered) in the fridge for a few hours before slicing and serving for a fudgier texture.
Keep blondies in an airtight container at room temp for 3 days and up to a week in the fridge.
Notes
Do note that blondies in general are sweet, and the white chocolate certainly makes them sweeter. This is intentional, as it mimics the sweetness of traditional Indian desserts. If you'd like to counter the sweetness, make sure to generously top with salt and/or serve chilled.I recommend measuring all your ingredients in advance before proceeding with this recipe so that you are ready to add the melted brown butter to the brown sugar while it's still hot. If the brown butter cools too much to room temperature before you add to the brown sugar, it can negatively impact the texture of the resulting blondies.