1.Preheat oven to 180 C (160 C fan-forced). grease a 20xm x 30cm rectangular slice pan. Line base and sides with 2 layers of baking paper extending paper 5cm over long sides.
2.Combine biscuit crumbs, macadamias and butter in a bowl. Press evenly over base of prepared pan. Bake for about 15 minutes or until golden; cool.
3.Sprinkle gelatine over the water in a small bowl. Microwave on high (100%) for about 15 seconds; stir to dissolve gelatine. Cool for 5 minutes.
4.Meanwhile, beat cream cheese in a bowl with an electric mixer until smooth. Gradually beat in condensed milk, sour cream, rind, juice and gelatine mixture. Pour over biscuit base; smooth top. Refrigerate for 1 hour or until firm.
5.Make passionfruit topping: Stir custard powder and 2 tablespoons of the water in a small saucepan until smooth. Stir in remaining water and sugar. Stir over medium heat until mixture boils and thickens. Stir in passionfruit pulp, then remove from heat. Sprinkle gelatine over extra water in a small bowl to soften; stir into hot passionfruit mixture; cool for 15 minutes. Pour passionfruit mixture over filling; refrigerate until firm.
6.Lift slice from pan; cut into pieces and drizzle with extra fresh passionfruit pulp.
You will need about 5 large, fresh passionfruit for this recipe. Slice can be made up to 3 days ahead; keep refrigerated.