Place caster sugar, passionfruit pulp and vanilla bean in a pan and bring to the boil; simmer for 1 minute. Add milk and cream, bring back almost to the boil, whisking gently, then remove from heat. Strain the seeds out if you prefer (but they look good and provide a little texture). If using gelatine leaves, soak them in cold water for 4 minutes before squeezing out excess water and adding the leaves (with none of the water) to the hot mixture. If using powdered gelatine, then sprinkle it over ⅓ cup warm water in a small bowl and leave to soak for 5 minutes, stir and then mix into the hot mixture making sure there are no lumps. Pour the mixture into eight 250 ml (8 fl oz) metal ramekins or one 8 cup mould. Cool, then cover and refrigerate to set (about 4 hours for ramekins or 8 hours for a large mould).
To unmould, dip the moulds briefly into a bowl ofvery hot water, then invert onto a plate.