Preheat oven to 200C/180C fan forced. Grease a 7cm-deep, 9 x 19cm (base measurement) loaf pan. Line the base and sides with baking paper, allowing the long sides to overhang. Line 2 large baking trays with baking paper. Coarsely chop half the pistachios and walnuts. Transfer to a bowl and set aside. Finely chop remaining nuts and transfer to a separate bowl.

Place 1 pastry sheet on each tray. Brush sheets with butter. Sprinkle with cinnamon, then finely chopped nuts. Drizzle over remaining butter. Bake for 8 minutes or until puffed and light golden. Pierce pastry sheets 2-3 times with a metal skewer. Use a baking tray to flatten sheets to 1-1.5cm thick. Bake for 8 minutes. Cool completely.

Stir cream, vanilla, 170g (¾ cup) sugar and 250ml (1 cup) milk in a large saucepan over medium heat. Bring to a simmer. Remove from heat. Combine cornflour, egg yolks and remaining milk in a jug. Whisk into cream mixture until well combined. Place over medium-low heat and cook, whisking, for 5 minutes or until thickened.

Cut each pastry sheet in half. Place 1 rectangle, nut-side down, over base of prepared pan, trimming to fit. Spread with one-third of custard mixture. Top with another rectangle, nut-side down. Top with half the remaining custard. Repeat with remaining pastry and custard, finishing with pastry. Place in fridge for 8 hours or overnight to set.

Place remaining caster sugar in a small saucepan with the lemon juice, honey, cloves, cinnamon stick and 80ml (1 /3 cup) water. Stir over medium heat until sugar dissolves. Increase heat to medium-high and simmer for 3 minutes or until thickened slightly. Strain. Discard cloves and cinnamon. Stir in the rosewater. Set aside to cool completely.

Turn slice onto a serving plate. Sprinkle over the coarsely chopped nuts. Drizzle with some syrup. Slice and serve with remaining syrup.