Instant Pot: Add the 1/2 gallon milk into your instant pot liner. Set the pressure valve to “sealing” or “steam” (depending on model).
Press the YOGURT button. Allow the pot to heat up to 180 degrees Fahrenheit. It will stop automatically when it reaches 180 degrees. Use a thermometer to make sure that the temperature is measured correctly.
Stovetop: Pour the 1/2 gallon milk into a large saucepan and heat over medium heat. Simply monitor the heat of the milk while you are warming it using a thermometer. Heat until the milk reaches 180 degrees and stir occasionally so that the milk does not burn.
Once the milk has warmed up and the pot has stopped, remove the liner from the pot (if using the stove method, remove the pot from the stove). Add the 1/4 cup vinegar into the milk and stir. Set a timer for 10 minutes and leave the milk.
When the 10 minutes are up, you should see that the milk has formed into clumps.
Use a cheesecloth to line a strainer. Pour the liquid into the strainer so as to remove the additional liquid and be left with only the cheese. Let the ricotta sit in the strainer for another 10-15 minutes to remove any leftover liquid.
Transfer the cheese into a bowl. Add the 1/4 tsp salt and stir. Enjoy!