Unwrap the filo sheets, however always keep covered as they dry very quickly. Cover with a damp tea-towel. These sheets are like vellum paper. On the packet "baklava sheets" must be written .
Preheat the oven to 160° Celsius. Grease a rectangular oven tray with butter.
Melt the remaining butter in a saucepan over low heat. The butter needs to be warm. You may want to re-heat it if necessary. If you notice a white part in the bottom of the melted butter, do not use it for baklava. If bubbles come up, skim and use elsewhere.
Lay half of the sheets of filo pastry, one at a time, into the tray, brushing each sheet with butter before adding the next. If the pastry is larger than your tray, break/cut to fit.
In a separate bowl, mix together the chopped walnuts, sugar, cinnamon and cardamon and spread this mixture evenly over the pastry in the tray. You can mix or replace the walnuts with nuts and/or chestnuts.
Layer up the remaining sheets on top of the walnut mixture, brushing each sheet with butter, as before.
When all the layers are on the tray, pour on top any butter that is remaining. Set aside to rest for 10 minutes.
Then, using a sharp knife, cut a diamond pattern into the layers of the pastry.
Place baklava in the preheated oven for approximately 40 minutes. It should be golden on top and bottom. Remove and rest for 2 minutes.
The syrup must have cooled by now. Slowly drizzle filtering the syrup into the cuts in the baklava and leave to cool. When filtered discard the cloves and the orange peels.