In a medium saucepan over medium heat, melt the butter, stirring gently as it foams and turns golden brown (about 6 to 8 minutes).

Remove the browned butter from heat and pour it into a heat-safe bowl. Allow it to cool for about 5 to 10 minutes.

In a mixing bowl, combine the cooled brown butter and brown sugar, stirring until smooth.

Add the egg, egg yolk, and vanilla extract, mixing until well combined.

Stir in the pistachio cream until fully incorporated.

Gently mix in the flour and salt until no dry streaks remain, then fold in the chocolate chips and chopped pistachios.

Preheat your oven to 350°F. Lightly grease an 8x8-inch baking pan or line it with parchment paper. Spread the batter evenly into the pan.

Dollop small amounts of pistachio cream on top and gently swirl with a knife. Add additional chocolate chips and pistachios on top if desired.

Bake for 20 to 25 minutes, until lightly golden around the edges and the center is set but still soft.

Allow the blondies to cool completely in the pan before slicing into squares.