Preheat oven to 200°C. Line 2 baking trays with baking paper. Cut the whole pastry sheet in half. Arrange 2 pastry halves, side by side, on a lined tray. Sprinkle with two-thirds of cinnamon sugar. Top with another sheet of baking paper. Place remaining lined tray over the 2 pastry halves. Place the remaining pastry sheet on top of the stacked tray and sprinkle with remaining cinnamon sugar. Bake, swapping trays and paper halfway through cooking, for 30 mins or until pastry is golden and crisp.
Meanwhile, to make the passionfruit cream, place the milk in a small saucepan over medium heat. Bring just to a simmer. Remove from heat.
Use an electric mixer to beat the egg yolks and sugar in a large bowl until thick and pale. Add the flour and passionfruit pulp and stir to combine. Gradually add milk, stirring to combine. Transfer mixture to the saucepan. Place over medium heat. Cook, stirring constantly, until custard boils and thickens. Transfer to a heatproof bowl and cover with plastic wrap. Place in the fridge for 30 mins to chill.
Use a clean electric mixer to beat mascarpone, cream and custard in a clean large bowl until firm peaks form. Transfer to a piping bag fitted with a plain 1cm nozzle.
Place 1 pastry half on a serving plate. Pipe one-third of passionfruit cream mixture over pastry half on the plate. Continue layering with the remaining pastry halves and passionfruit cream, finishing with the passionfruit cream. Top with the pineapple, mango, lychee and melon. Spoon over the passionfruit pulp. Serve immediately.