Place the halved dates between two sheets of greaseproof paper. Using a rolling pin, roll firmly to flatten into a rectangle about 13cm x 25cm/5in x 10in. Lay the greaseproof-wrapped date sheet onto a baking tray and leave to set in the fridge for 30-40 minutes.
Meanwhile, make the frangipane. Mix the rosewater, sugar and water in a small pan and heat gently until the sugar has dissolved. Add the ground almonds and beat to make a smooth, thick paste.
Put the soya margarine into a small pan and heat gently to melt. Then pour into a bowl and set aside until needed.
To assemble, take the date sheet out of the fridge and set it on a flat board. Peel off the top layer of greaseproof paper, trim the edges to make them neat and cut the date sheet into three rectangular pieces, each about 12cm x 8cm/4½in x 3¼in. Divide the frangipane between the date pieces, spreading it down the length in the middle of each and leaving a small gap at each end. Sprinkle over the pomegranate seeds and roll each piece into a long sausage shape. Using a sharp knife, trim the ends and cut each roll into four pieces.
Preheat the oven to 190C/375F/Gas 5. Take a piece of filo pastry and brush the edges with the melted margarine. Roll up a date piece in the pastry, twisting each end like a wrapped sweet to seal. Trim the ends with a sharp knife. Repeat with the remaining pastry and date pieces, then transfer to the fridge for 15 minutes.
Meanwhile, scatter the chopped pistachios over a non-stick baking tray and roast in the oven for 6-8 minutes, or until lightly toasted. Remove from the oven and reserve for the garnish.
To finish the date parcels, heat the sunflower oil in a deep pan to 180C/350F. (CAUTION: Do not leave the hot oil unattended.) Drop an off-cut of pastry into the oil; if it sizzles and rises to the top, the oil is hot enough. Fry the date parcels in batches for about four minutes, or until golden-brown, then drain on kitchen paper. Serve garnished with the pomegranate seeds and toasted pistachios.