I used to make this years ago as a kid and came across the idea again quite recently. You'll need a thermometer - I used a meat thermometer, which worked perfectly. Acknowledgements to "Making Artisan Cheese", by Tim Smith, for the reminder, and specifically for the figure of 74C.
You will need
A meat thermometer or similar
2 litres full cream milk, either homogenised or not.
60ml lemon juice
Heat the milk to 74C, stirring frequently to prevent sticking or burning
Then, take the pot off the heat and stir in the lemon juice.
Let it rest for 15 minutes. (You get a different curd depending on whether you start with homogenised milk or not.)
Pour the mix into a muslin or cheesecloth lined colander (no cheesecloth so I used a clean smooth-surface teatowel) with a large catch bowl underneath and place in the refrigerator for an hour, or until the whey stops dripping. (The bowl needs to accommodate about 1.5 litres of whey.)
Remove the cheese from the fridge, and place in a bowl. Add salt to taste plus any flavourings or herbs. Will keep for a week in the fridge in an airtight container.
Makes a pleasant lightly lemony spread, and costwise for materials works out a little under 80% of the same weight of commercially bought cottage cheese - about 450-500g - but it's a bit denser in texture, so probably about the same value overall. Possibly better to compare it with cream cheese.
This also provides you with about a litre and a half of a refreshing whey drink, which you can improve on by adding another squeeze of lemon. Or you can use it, slightly warm, as liquid in a bread recipe.