Brown the Butter:

• Melt butter in a small saucepan over medium-low heat, stirring occasionally.

• Cook until the butter becomes foamy and the milk solids turn golden brown (about 5 minutes).

• Immediately pour into a small heatproof bowl and refrigerate until solidified (45 minutes to 1 hour).

Prepare the Dough:

• Preheat oven to 350°F (175°C).

• In a medium bowl, sift together flour, baking powder, salt, and baking soda.

• Using an electric mixer, beat chilled browned butter, brown sugar, and granulated sugar on medium-high speed until light and fluffy (about 3 minutes).

• Add egg and vanilla extract, then beat until well combined (about 15 seconds).

• On low speed, gradually add flour mixture, mixing until just combined (about 1 minute).

• Fold in white chocolate, pistachios, and ¼ cup dark chocolate.

Shape & Bake the Cookies:

• Roll dough into 1-inch balls (about 1 tbsp each).

• Place into a 24-cup non-stick mini muffin tray.

• Bake for 12-14 minutes until edges are set but centers remain soft.

• Immediately press down the center of each cookie using a rounded 1-teaspoon measuring spoon to create a well.

• Let cool in the muffin tray for 15 minutes, then carefully remove and transfer to a wire rack to cool completely (20-30 minutes).

Fill & Decorate:

• Microwave remaining ¼ cup dark chocolate in 30-second intervals until fully melted.

• Spoon 1 teaspoon pistachio cream into each cookie cup.

• Drizzle melted chocolate over the top.

• Sprinkle with chopped pistachios.

• Refrigerate for 5 minutes until chocolate is set.