In a thick bottomed pan, pour all but half a cup of milk and add sugar to it. Heat it, stirring in between to dissolve the sugar. Let it simmer for 2-3 minutes on low heat.
To the reserved half cup of milk, add 4 tbsp corn flour. Mix until no lumps remain and add it slowly and steadily to the simmering milk. Stir continuously to avoid any lumps.
Cook it for some more time until the milk thickens and starts to coat the back of the spoon. Take off the heat and let it cool. Stir well to prevent any skin from forming at the top.
Once it is cool, stir in the fresh cream and vanilla essence. Using a hand mixer, beat until its incorporated well. If you are using pureed fruits, you can mix it in now.
Transfer this to a flat container with a lid and freeze it until set. Take out and beat the ice cream again. Freeze it again until its set. Repeat this once every 2 hours for 3-4 times.
After the last mixing, you can add the crushed cookies or chocolate chips, if you are using. Mix it in using a spoon. Freeze overnight or until its set.