Put the Gelatine Leaves in a shallow dish and cover with cold water.
Leave to soak for 10 minutes.
Meanwhile, heat the cream gently with 65g (2 1⁄2 oz) sugar, stir until dissolved, then heat to just below boiling point.
Remove from the heat.
Drain the Gelatine Leaves, and squeeze out the excess water.
Stir into the hot cream until melted.
Leave to cool completely then strain through a sieve into a jug and stir in the Vanilla Extract.
Pour into 4 x 125ml (4 1⁄2 fl.oz) dariole moulds, jelly moulds or ramekin dishes.
Allow to chill for at least 2 hours until set.
For the sauce, put the Arrowroot in a small saucepan.
Put the lemon juice in a measuring jug and make up to 250ml (9 fl.oz) with cold water.
Blend a little bit of the liquid with the Arrowroot to make a paste.
Add the remaining sugar and stir in the remaining lemony water.
Heat gently, stirring, until the mixture boils and thickens slightly.
Leave to cool then add a few drops of Gel Food Colour and flavour with rose water to taste.
Cover and chill until required.
To serve, dip the moulds in very hot water for a few seconds to loosen the Panna Cottas and invert on to serving plates.
Serve with a little sauce spooned over and decorate with pomegranate seeds and rose petals.