01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - Process pistachios in a food processor until finely ground. Add softened butter and powdered sugar, blending until creamy. Incorporate egg, vanilla extract, flour, and salt, processing until mixture is smooth and fully combined.
03 - Cut each croissant horizontally, keeping the back edge intact to create a hinged opening.
04 - Lightly brush the inside of each croissant with simple syrup to maintain moisture during baking.
05 - Spread a generous layer of pistachio cream inside each croissant. Close and arrange on the prepared baking sheet.
06 - Apply a thin layer of pistachio cream over the top surface of each croissant. Sprinkle evenly with chopped pistachios.
07 - Bake for 15 to 20 minutes until surfaces are golden brown and the filling is set.
08 - Allow croissants to cool briefly on the baking sheet. Dust generously with powdered sugar before serving.