This pic is actually the one I took while I made Patties for Rasmalai, but the process is same for Rasagulla too, but that will be a beautiful round shape :)
Milk - 4 cups
Sugar - 2 cups (can be more per taste)
Lime Juice - 2 spoons
Boil the milk on a medium flame.
Add 2 spoons of lime juice mixed in a spoon of water and pour this little by little into the boiling milk. Keep kindling the milk.Once the lime is poured, milk will start breaking and will become greenish liquid. (Add more lime if only the milk is not broken still )
Switch off the heat immediately.
Use a muslin cloth/ filter / any thin cloth to filter off this malai part of the milk.
Sprinkle / splash some cold water on the malai to stop the Milk-breaking process completely.
Let the malai to dry up fully in the muslin cloth/filter for about 30 mins. It should become fully dry without any liquid.
Meantime, In a pressure pan, heat 4 cups of water adding 2 cups of sugar into it. Let the sugar boil completely.
Knead the malai very finely using your hand. Make few balls out of this malai.
Add the malai balls into the boiling sugar water and keep it for one whistle (if you are using a normal pan, you can keep for about 15-20 mins).
The balls would have doubled its size and would have obsorbed the sweetness well. Switch off the heat, Rasagullas ready :)