The day before, preheat the oven to 180C/160C F/Gas 4. Put the pistachios, almonds and cinnamon in a food processor and blend until the nuts are coarsely ground. Stir in the sugar and set aside, reserving 4tbsp of the mixture for serving. Lightly grease a 23cm square cake tin. Cut each pastry sheet in half and trim it so it fits into the tin. Press eight of the sheets into the tin, brushing each one with butter before layering them. Scatter the nut mixture over and top with the remaining pastry sheets, brushing each one with melted butter. Brush any remaining butter over and bake for 20 minutes.
Reduce the temperature to 170C/150C F/Gas 3 and bake for a further 20-25 minutes until the pastry is crisp and golden. Remove from the oven and prick the surface all over using a skewer. Just before the end of the cooking time, prepare the syrup. Put the lemon zest and juice, honey and 100ml water in a pan and heat gently until boiling. Simmer for 5 minutes, remove from the heat and stir in the rose water. Immediately pour three-quarters of the honey syrup over the cooked baklava and leave to go cold in the tin. Reserve the remaining syrup for serving.
Turn the pastry out of the tin and cut in half. Lightly grease a 1kg loaf tin. Spread a third of the softened ice cream into the base of the loaf tin and place one half of the baklava on top. Repeat with another third of the ice cream and remaining baklava and finally the remaining ice cream. Smooth the top, cover with cling film and freeze overnight.
The next day, remove from the freezer 20 minutes before serving. Turn out and cut into slices. Drizzle the reserved syrup over and decorate with dried rose petals and the reserved nut mixture.
Recipes and styling by Louise Pickford, photography by Unsplash/Nina Ha; Ian Wallace
