Store-bought ricotta can’t hold a candle to creamy, rich homemade cheese. You don’t need any special equipment, and the YOGURT setting on most Instant Pot models gently heats the milk to the perfect temperature, so there’s no worrying about scorching the milk on the stove. If you don’t have a YOGURT setting, heat the milk on SAUTÉ on the NORMAL/MEDIUM heat, stirring occasionally, until a thermometer reaches 190°F before proceeding as directed. Ricotta is only as good as the milk you use to make it, so buy the best milk you can find and make sure that it isn’t ultra-high temperature (UHT) pasteurized milk. The UHT process changes the proteins in the milk and will prevent it from forming curds. You can use fresh lemon juice to make the milk coagulate, but I find it easier to add citric acid, which you can find at spice shops or buy online. The liquid left over in the pot after cheese making is called whey, as in Little Miss Muffet’s “curds and whey.” It’s full of beneficial probiotic organisms, amino acids, vitamins, and minerals, so don’t pour it down the drain! You can use it in soups, sauces, and smoothies as a neutral-flavored liquid that adds a big nutritional boost.
Pour the milk into the Instant Pot and cover with a regular pot lid that fits on top of the Instant Pot. Select the YOGURT function and adjust until the digital display reads BOIL. When the cooking time is up, remove the lid, being careful not to let any condensation drip back into the pot.
Remove the inner pot from the appliance and place it on a trivet. Add the lemon juice or citric acid and stir gently a few times (overzealous stirring will yield cheese with a grainy texture) until you begin to see the milk coagulate—there will be a separation between bright white chunks of curd and thin yellowish liquid whey. This will take about 30 seconds. Stop stirring and let the mixture stand for 5 minutes.
Line a fine-mesh sieve or colander with cheesecloth or a clean, thin cotton-sack towel and set it over a large bowl. Carefully pour the cheese and whey into the colander.
For moist, creamy ricotta, let the cheese drain for 5 minutes. For firmer ricotta, allow the cheese to drain forup to 4 hours at room temperature. When the cheese is done draining, stir in the salt (if using). Save the whey for another use (see Headnote).
Transfer the cheese to an airtight container and refrigerate. (The ricotta can be stored in an airtight container in the refrigerator for up to 5 days or in the freezer for up to 3 months.)