Mix Cocoa powder and custard powder. Add 1/4 cup warm water and mix well without any lumps. Keep it aside.
Boil the milk.
When it starts to boil, reduce the flame and pour condensed milk and previously prepared cocoa custard mix.
Keep the flame in low and stir continuously until it starts to thicken.
Turn off the flame, let it cool and pour it into a pudding tray. Garnish with some crushed chocolate wafers and refrigerate for 4-5 hours and serve chilled.