Unroll the pastry and spread with raspberry jam. Roll up the pastry lengthways and cut the pastry in half down the middle of the roll lengthways.
Interlace the two rolls and shape into a ring. Place the pastry wreath onto a lined baking tray. Brush with beaten egg and bake for 40 minutes Until golden and puffed. Reduce the oven to 140C and bake for a further 10 minutes to cook through.
Remove from the oven and set aside to cool.
Whisk together the sifted icing sugar and lemon juice. Drizzle the icing over the wreath. Scatter over chopped pistachio nuts and serve.