Mix together the sugar and cornflour in a large saucepan. Whisk in the milk and rosewater. Try to avoid getting any lumps. combine the sugar and cornflour in a large saucepan then. Cook over low heat, stirring continuously, until the mixture thickens and comes to a simmer. Turn the heat down as low as possible so the mixture is barely simmering and cook for 25–30 minutes, stirring continuously. By the end of the cooking time the custard will be very thick and paste-like. Pour the hot custard into a serving dish or dishes and place in the fridge to cool.
Whilst the custard is cooling put the sugar, glucose and water in small saucepan. Bring to the boil then reduce the heat and simmer until the syrup has thickened. Take off the heat and leave to cool. Once cool stir in the rosewater.
Remove the baked custard from the fridge and drizzle with the rose water syrup. Decorate with rose petals to serve.