For the record, this is mum's exact recipe, but even I can't make it as well as she does. Something about Siham's special baking trays or her hands.
For the correct consistency of the syrup, have a look at my knafeh recipe.
Melt the butter on a low heat, so that the milk solids do not boil and mix in with the pure butter.
Slice lines into the filo, vertically and diagonally, to create diamond shapes. There is no need to cut all the way into thge bottom layer. This may damage your tray and isn't necessary for the butter and sugar to soak through.
Pour the butter/ oil evenly over the pastry. Be sure not to pour the milk solids in (the white part at the bottom of the melted butter). You will be left with black, burnt spots on the surface of the baklawa.
Pour the sugar syrup over the hot baklawa. You should hear a sizzle when the hot baklawa and the cool syrup make contact.
Sprinkle ground pistachio nuts and optional rose petals on top of baklawa. I use a mortar and pestle to crush the pistachios but you could use a food processor or even a rolling pin.