In a small mixing bowl, combine ½ cup warm milk, cocoa powder and corn flour. Mix well without any lumps. keep it aside.
Heat remaining 1.5 cups milk and add sugar sugar, vanilla essence and prepared chocolate milk mixture.
Stir continuously to prevent lumps forming. Keep stirring and cook on low flame until the mixture thickens.
Turn off the flame and let it cool completely. This will thicken more as it cools.
Add the chopped fruits to the cooled chocolate custard and mix everything well.
Refrigerate it and serve chilled.
You can also chill the custard first and add the fruits before serving.
Notes
I have used papaya, apple, banana, pomegranate and berries. You can use any of your favorite fruits except watermelon to make this custard.You can substitute the corn flour and vanilla essence with vanilla flavored custard powder.