01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - Grind pistachios finely in a food processor. Add softened butter and powdered sugar, blend until creamy. Incorporate egg, vanilla, flour, and salt. Process until smooth and fully combined.
03 - Cut each croissant horizontally, leaving a small hinge attached to prevent complete separation.
04 - Brush the inside of each croissant with simple syrup if using, which helps maintain moisture during baking.
05 - Spread a generous layer of pistachio cream inside each croissant. Close and arrange on the prepared baking sheet.
06 - Coat the exterior of each croissant with a thin layer of pistachio cream. Sprinkle chopped pistachios over the top.
07 - Bake for 15 to 20 minutes until golden brown and the cream filling is set.
08 - Allow to cool briefly, then dust with powdered sugar before serving.