Sift cocoa and icing sugar together and mix in a bowl.
Have a greased pan ready.
In a thick bottom pan, take the condensed milk, cook on low heat, after couple of minutes add the butter. With a wooden ladle, keep stirring continuously, making sure the bottom doesn't get burnt.
It takes about 10 mins on high flame to reach the ball stage consistency. You are sure you are done when you see the mixture starts to come together and you can see the bottom pan revealed as you stir.
When you are sure the mixture reached the consistency, pour into the greased pan, spread it well for it to cool down.
When it reaches the room temperature or atleast safe for you to handle, start making balls and keep it to rest.
Don’t let it rest for long as it might not get properly coated. Once you are done making a perfect balls/laddos, roll them in the cocoa icing sugar mix until it is completely covered.
Serve these in a small paper cups or cupcake liners else store in a tight box.