Heat the butter and briefly braise the finely crumbled kadaif in it with 1 tbsp sugar.
In an oiled tray, pour 1/2 the kadaif, distribute the walnut mixture over it. Cover with the remaining kadaif and bake in a preheated 338°F (170 °C) oven.
Take the baked cake out and leave to cool.
Make a syrup from the sugar and water, leave it to boil for 5 min. Remove from the stove, pour the still-hot syrup over the cake, distributing it evenly.
Cover the cake with a tray and let it take in the syrup for 4-5 hours.