Combine the milk, heavy cream, and salt in a medium pot. Heat on medium, stirring occasionally to prevent scorching (you can kick up the heat to speed up the process if you don't mind stirring attentively the whole time), until the milk is steaming just below a simmer and registers 180 degrees F on an instant-read thermometer.
Off the heat, stir in the vinegar. Immediately, the milk will start to separate. Let the mixture sit for 5-10 minutes.
Line a colander with a double layer of cheesecloth (coffee filters work great, too, if you stagger them or they are large enough) or open a nut milk strainer bag over a large bowl. Spoon in the large curds first if you want to avoid splatters and follow it up by pouring in the rest of the mixture.
If using a nut milk bag, carefully lift it up and out of the bowl and hang it so it can continue to drip into the bowl. Let the ricotta strain for 10-60 minutes, depending on the texture you are after. I usually go with right around 15 minutes for super creamy ricotta.
Scrape the ricotta out of the colander or bag; use immediately or refrigerate up to a week or so.
Notes
Milk: I've made this once with 1% (never with skim or non-dairy milks - lower fat milks may not separate as well into the curds and whey) and my favorite combination is the one I've listed in the ingredients. Feel free to play around with the type of milk/cream used.Whey: don't discard the whey! I use leftover whey in pancakes (in the place of buttermilk) and in my homemade bread (subbing it in for the water), among other things.