In a large pot, combine the milk and cream and heat it over medium heat. Use a thermometer to monitor the temperature, and heat it until it reaches 175°F.
Once the milk and cream reach 175°F, remove the pot from the heat and add the salt and lemon juice or vinegar. Stir the mixture gently to combine.
After adding the acid, let the mixture sit for 5-10 minutes. During this time, the acid will cause the milk proteins to coagulate and form curds.
After the curdling process is complete, place a colander lined with cheesecloth over a mixing bowl. Carefully pour the mixture into the colander, allowing the whey (the liquid portion of the mixture) to drain into the bowl.
Let the cheese drain for at least 6 hours, or overnight, in the refrigerator. The longer the cheese drains, the firmer it will become.
Once the cheese has drained, transfer it to a mixing bowl and use a hand mixer or stand mixer to beat it until it's smooth and creamy.
Transfer the cream cheese to an airtight container and store it in the refrigerator for up to two weeks.