1. Mix the cornflour, cream of tartar, and 200ml water in a non-stick saucepan until smooth.
2. Add the sugar and gently dissolve over low heat, stirring constantly.
3. Once the sugar has dissolved, increase the heat and bring the mixture to a boil. Then, reduce to a simmer without stirring for about 15 minutes or until the mixture reaches the soft-ball stage (115°C on a sugar thermometer).
4. Remove from the heat, and stir in the rose water and optional food colouring.
5. Pour the mixture into a shallow, cornflour-dusted tray and leave to set at room temperature for at least 4 hours, or overnight.
6. Once set, dust a surface with icing sugar, turn out the Turkish Delight, and cut it into cubes. Dust all sides of the cubes with more icing sugar to prevent sticking.

Storage: Turkish Delight can be kept in an airtight container, layered with parchment paper and dusted with icing sugar, for up to 2 weeks.