Start by lining a container with cling film.
Mix the raspberries with the icing sugar and push through a sieve.
Add the egg yolks to a mixing bowl and whisk together.
Put the water and sugar into a heavy saucepan and let the sugar dissolve over a low heat. Increase the heat until the mixture reaches 120C/248F.
Pour in the sugar syrup and whisk continually until all of the syrup has been incorporated. Keep whisking until the mixture is falling in ribbons.
Gently fold in the raspberry purée and lightly fold in.
Whip the cream into soft peaks and fold the raspberry mix into it.
Pour the mixture into the container and freeze for 24 hours.
To serve, remove the raspberry parfait from the freezer, unwrap the film and place on a plate.
Leave for a couple of minutes before slicing, then serve with some fresh raspberries.