Step 1

Fill a pot with the milk. Stir in salt, if using. Heat over medium heat until milk registers 185°F (85°C) on an instant-read thermometer. Add vinegar or lemon juice and stir briefly to incorporate. Curds should begin forming almost immediately; stop stirring as soon as they've formed throughout the pot.

Step 2

Without stirring, continue to hold curdled-milk mixture at 185°F for 20 minutes. It's okay if the temperature fluctuates down to 175°F (79°C) or up to 190°F (88°C), but try to keep it in that zone for the full 20 minutes.

Step 3

Line a fine-mesh strainer with paper towels or cheesecloth. Using a slotted spoon, transfer curds to strainer and let stand until excess liquid has drained away. Exactly how long to let it drain depends on whether you want a moister final product or a drier one. Do not try to pour all the milky liquid through the strainer, as this will clog it and prevent the liquid from flowing through.

Step 4

Drained ricotta can be refrigerated, covered, for up to 2 days, though it is best when freshly made.