In a saucepan, take the corn flour, add the milk and mix well. Cook on medium flame. After few seconds, add sugar and cook till the mix starts boiling. This takes about 2 to 3 mins. Allow it cool completely.
Take the corn flour liquid to a mixer, add the chopped pineapple and pulse to a smooth paste.
Transfer to a bowl, add condensed milk, mix everything well together.
Transfer to the serving bowl and freeze for 10 mins.
Serve with diced pineapple pieces on top.