Whisk together egg yolks and water in a small bowl.
Combine sugar, cinnamon, and cardamom.
Carefully roll each sheet of puff pastry into a 9 1/2" square on a lightly floured work surface. Brush each sheet with egg wash, and sprinkle with 2 tablespoons sugar mixture. Sprinkle chopped pistachios evenly over 1 sheet, leaving a 1/4" border; top with remaining sheet, sugared side down. Firmly press edges to seal. Brush top of pastry with melted butter; sprinkle with remaining sugar mixture. Cut pastry into 3/4"-thick strips, using a pizza cutter. Twist each strip 3 times, and place 2" apart on lightly greased baking sheets.
Bake at 400° for 19 minutes or until golden. Remove from pans immediately, and cool on wire racks.
Note: To reheat pastry twists, bake at 450° for 5 minutes or just until heated. Cool. (As they cool, they crisp up.)