Set aside 3 oz (100g) of shelled pistachios for the topping.
Mix all the remaining nuts. Stir in 4 tablespoons (50g) of butter, rose water or orange blossom, cinnamon, and sugar. Mix well and set aside.
Preheat oven to 350F/180C.
Bake for 30 minutes at 350F/180C, and then 30 minutes at 300F/150C.