There is no substitute for fresh home-made paneer especially for making Indian cheese-based desserts such as Channa Payesh, Ras Gulla, Ras Malai, etc or the quite popular savory dishes called Palak (spinach) and Mattar (peas) Paneer. Paneer can also be used in place of ricotta cheese. Making fresh paneer is not difficult at all; one just has to plan ahead and start the process a day or two ahead so that the paneer is recipe ready.
The science of making paneer is pretty simple; heat and an acidic agent are utilized to denature and coagulate most of the proteins from the milk. Milk is heated first and lemon/lime juice or citric acid are used to coagulate the protein. Vinegar could also be employed for curdling the milk but it leaves behind its flavor which quite ruins the delicate taste of the paneer in my opinion.
When the curds (paneer/milk protein) are strained out, the fluid left is called whey. The whey is still nutritious and can be used in cooking and baking. I recall that when we were ill with fevers or flu as children, we were given warm sweetened 'whey water' as it was easier to digest than whole milk.
Makes about 2 cups
2 quarts/liter milk
1 or 2 lemons/limes
Heat the milk slowly in a large sauce pan until quite hot.
Turn the heat down and stir in the juice of 1 lemon or lime without any pulp.
Keep stirring and heating and the proteins will coagulate into small lumps.
If the whey is still milky, add more of the lemon/lime juice while stirring until the whey becomes clear.
Turn off the heat and let cool for about 20 or 30 minutes.
Line a colander or strainer with a large muslin like cloth and set it over another container large enough to catch all of the drained whey without overflowing.
Pour the curds and whey into the cloth lined colander very carefully and let it sit until most of the whey has drained and the curds are cool.
Set aside the whey for cooking/baking or discard it.
Loosely tie the cloth and set the colander over a bowl, cover, and set it in the refrigerator to drain well - this might take several hours or overnight.
At this point you can decide whether to make a slab for cutting the paneer into pieces or not.
If you want to make a slab, flatten the cloth covered paneer and set it on a plate and put a heavy object on top and leave for several hours for it to set.
If you are not making a slab, just scrape off the paneer from the cloth and proceed according to the recipe.
Once the paneer is ready, remove from the cloth, and keep it chilled in a covered container until ready to use.
Paneer will stay fresh for a few days in the refrigerator.