Heat milk in a thick bottom large pan.
When milk is about to boil, lower the flame and slowly add vinegar one spoon at a time. Stir the milk gently.
Later increase the flame and milk will be curdled.
Switch off the gas and allow it to cool.
Pour the curdled milk into a muslin cloth, you can collect the whey for later use.
Now run the curdled milk under cold water to remove the flavor of vinegar.
Squeeze the excess water and tie the loose ends of muslin cloth and hang it for half an hour to drain the excess water.
After that take the chana in a plate and mash it using palm until the texture becomes smooth.
Meanwhile, take grated jaggery in a wok and add ½ cup of water and boil for few minutes. Jaggery should be melted properly and there should not be any lump. Keep aside and allow it to cool.
Now take a mashed chana in a wok and switch on the gas.
Add the melted jaggery into the chana and slowly mix it by stirring under low to medium flame.
Once the jaggery is combined and the mixture starts leaving the sides of the wok, switch off the gas and allow it to cool.
After cooling take the mixture in a blender and blend it (few seconds) to get smooth texture. Instead of blending you can also knead it using palm.
At this stage, if the texture of the sondesh is soft and contains moisture, take it in a wok and heat up for few minutes. If not then Sondesh is ready.
Now you can grease the moulds with ghee and shape them as you want and garnish with raisin.