Wash and roughly chop your fruit (removing the strawberry hulls if necessary), place in a large pan and cover with the water. Bring to the boil then simmer, until the fruit has started to break down, generally around 20 minutes or so.
Remove from the heat and strain the juice through a sieve or muslin. Discard the fruit pulp, and then place the juice back on the stove with the sugar, stirring until it has fully dissolved.
Now turn down the heat to medium, and slowly pour in the cornflour and water mixture, stirring continuously until the fruit juice thickens into a silky smooth, gel-like syrup.
Pour into individual serving dishes or one large bowl, and allow to cool before serving with a dollop of cream and a sprinkle of sugar if necessary.