Preheat the oven to 180°C and roast the walnuts for 8-10 minutes in a baking tray lined with greaseproof paper.
As soon as they cool, place them in a blender with the demerara sugar, the cinnamon and the cloves and blend.
Cut a piece of greaseproof paper to fit the size of the baking tray that you are going to use (30x40 cm)
And use it to cut the filo pastry sheets to that size (whatever is left out you can use it so that one packet is enough to make 30 layers).
Place the filo pastry sheets one by one into the baking tray and brush with butter forming 10 layers.
Pour in half of the filling and distribute it evenly all around.
Carry on with 10 more of the filo sheets, spread the rest of the filling and finish off with the last 10 filo sheets.
Cut the baklava into diagonal pieces and bake at 150°C (using the fan) for 1 1/2 hour.
A little before you take the baking tray out of the oven, prepare the syrup which you let boil vigorously for 7-8 minutes.
Pour the hot syrup over the baklava as soon as you remove it from the oven.
