Carefully separate the sheets of pastry, cut to the right size for the tin and cover with a damp cloth.
Finely grind the walnuts and almonds in a grinder.
Grind the pistachios also, but not so finely.
Beat the egg whites until stiff, then fold in the honey, nuts, cinnamon and rose water.
Brush the baking tin with butter and fill with alternate layers of pastry and nut mixture, brushing each sheet of pastry with butter.
Finish with a sheet of pastry.
Bake in a preheated oven (200°, middle shelf) for about 30 minutes.
Meanwhile place the sugar in a pan with 250 ml water and bring to the boil.
Boil for 1 minute, remove from the heat and cool slightly.
Then mix in the lemon juice.
When it is ready take the baklava out of the oven and while still hot, gradually soak with the syrup.
Leave to cool.
To serve cut into squares and garnish with redcurrants.