Heat oven to 180C/160C fan/gas 4. Put the peach halves in a gratin dish in a single layer without too much space around them (otherwise the apple juice will simply reduce and burn).
Crush the pistachios roughly using a pestle and mortar, then mix in the lemon zest, sugar, egg and 1 tsp orange blossom water. Fill the cavity of each peach with this stuffing, mounding it over the top if you have too much.
Mix the apple juice with the rest of the orange blossom water and pour it around the peaches. Bake for 30-45 mins, depending on ripeness. The peaches should be tender and slightly caramelised on the top.
Whip the cream until it holds its shape, then add the orange zest and sugar, and taste for sweetness. Stir in 1/2 tsp of the orange blossom water and taste. Add more if you like, but be careful not to make the cream too perfumed.
Serve the peaches at room temperature, with a little icing sugar sifted on top, some of the cooking juices spooned around and the cream on the side.