Place the 250g castor sugar and water in a pan and bring to the boil. Once boiling leave to boil for 5 minutes, bang on, no more no less. I use a small digital timer.
Place the egg yolks into a mixing bowl, and once the sugar and water have been boiling for 2 minutes, set the machine to medium speed.
At 5 minutes, take the sugar and water off the stove, turn the machine up to full speed, and pour onto the egg yolks. Whisk until thick, foamy and cold.
Liquidise the fruit and 150g castor sugar together and strain through a fine sieve.
Remove the egg yolk mixture from the machine.
Carefully fold through the lightly whipped cream.
Partially fold through the fruit puree and freeze, beat overnight.