Melt butter. Place a sheet of dough on a work surface and lightly sprinkle with butter. Continue with the remaining sheets, leaving the top sheet dry. Cut the stack of dough sheets into 8 x 8 cm (approximately 3 x 3 inch) squares. Cover with a lightly damp towel. Chop the walnuts.
Beat egg whites with 1 tablespoon lemon juice until stiff. Add 100 grams (about 1/2 cup) sugar and beat again until stiff. Fold in walnuts and almonds. Stir in 1 tablespoon rosewater. Place 1 tablespoon of filling in the center of each dough square. Pinch the edges over the filling. Place them on a greased baking sheet. Bake in an oven preheated to 180°C (approximately 350°F) for 30 minutes.
Simmer the remaining sugar and 250 ml (approximately 1 cup) of water for about 10 minutes. Stir in the remaining lemon juice and rose water. Let cool. Drizzle over the warm cookies. Sprinkle the pistachios over the cookies. Let cool before serving.