Every once in a while, some milk goes bad before one of us drinks or uses it. I refuse to throw away any food item if it can be used for something, and the same goes for milk. As soon as you discover that your milk has gone a little rancid, turn it into cheese.
In Indian food, this cheese is called paneer. Others call it farmer cheese. Either way, it's super-easy and has the consistency and properties of good tofu. I love tofu but am reluctantly coming to terms with my soy intolerance, so this is a perfect substitute.
In a large pot, bring however much milk you have to just under a boil. It should not quite bubble, but be careful not to scald the milk. As soon as it looks like it wants to boil, turn off the heat and add some vinegar or lemon juice.
I used about 3/4 of a gallon of milk and maybe 1/4 cup of vinegar. Mix it gently and it'll start to separate. Ew. This is good, though.
After stirring occasionally for about 10 minutes, I strained the curds out of the whey with cheesecloth lined in a little strainer.
Then I let that sit for about an hour until the liquid drains out. Give that a little squeeze, and transfer the cheese to another container or go ahead and cook it right away. I already had other plans for dinner to make that night, so I saved it to use later.
Don't let any milk go to waste! Presumably, this only works with actual dairy and not vegan milks.