Paneer is one of the oldest of cheeses and has been made since milk started turning sour. Born in Persia (پنير) and raised in South Asia (पनीर) and Turkey (peynir), paneer is often made daily in households and is a common ingredient in the cuisines of Iran, India, Pakistan, Turkey, Azerbaijan, and Tajikistan. Credit to BBC and fxcuisine as my source sites.
1 litre full cream milk
1 to 2 tbsp lemon juice (15-30 mL)
1. Gently warm the milk. When it starts boiling add the lemon juice and stir well with a wooden spoon. Don't use a metal spoon because this will react with the lemon juice and influence the taste. The milk will start to curdle.
2. Continue stirring and after five to seven minutes the curds* will have totally separated from the whey*. Those curds will be your cheese.
3. Line a large bowl with muslin, cheesecloth, or any clean cotton cloth (I used an old white shirt) and pour the curds and whey. The whey will filter out and leave the curds in the cloth. Allow it to drain for around 30 minutes.
4. When it's cold enough to handle, squeeze out more of the whey by wringing it through the cloth. The more whey you squeeze out the dryer and harder your paneer will be.
5. Place your yet unformed paneer between two plates, press it with a weight, and leave for a few hours. This will squeeze out yet more whey and form the paneer, filling in the air holes. As is obvious in the picture, I skipped this step thus my very crumbly paneer.
My one litre of milk produced a fist-sized amount of paneer (I guess around 150g to 200g) and about 900mL of whey. As it wasn't fermented, the paneer was expectedly bland but it still had that hint of milky/cheesy flavour which will only get stronger with age. The whey was essentially cheese-flavoured water which I still keep in my ref pending some idea on how to use it. I ate around half of the paneer on its own and the other half I used in an omelette with Vienna sausages.
* Milk is basically an emulsion of butterfat and water held together by proteins (primarily casein, alpha-lactalbumin, and beta-lactoglobulin). When milk is acted upon by heat and acid (in this case the lemon juice), some proteins curdle with the butterfat to form the curds (which, when formed, become cheese) while some proteins stay dissolved in the water to form the whey (the yellowish liquid in the picture). This process is called acid coagulation, as opposed to the more frequently used method of coagulating milk using rennet (enzymes extracted from mammalian stomachs).