In a medium saucepan over medium heat, melt the unsalted butter, stirring continuously until it turns golden with brown bits forming, about 6 to 8 minutes.

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

In another bowl, whisk together the warm brown butter and brown sugar until smooth.

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

Stir in the pistachio cream until evenly blended.

Gently fold in the flour and salt, taking care not to overmix.

Fold in the chocolate chips and chopped pistachios.

Preheat the oven to 350°F (175°C) and prepare an 8×8-inch baking pan with parchment paper or grease it lightly.

Spread the blondie batter evenly into the pan. Add dollops of pistachio cream on top and create swirls using a knife. Optionally, sprinkle extra chocolate chips and pistachios.

Bake for 20 to 25 minutes until the edges are golden and the center remains soft.

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