1. Mix the cornflour in half cup of cold milk and keep aside.
2. Bring the remaining milk to a boil in a non-stick pan and add the cornflour mixture.
3. Stir continuously and simmer over a slow flame till it coats the back of a spoon.
4. Cool completely. Add the sugar substitute and the strawberries and pour into an air-tight container.
5. Freeze for 4 to 6 hours.
6. Blend in a blender till it is slushy and pour back into the air-tight container. Freeze till the ice-cream is set.