Set a fine-mesh sieve over a deep bowl. Dampen 2 pieces of cheesecloth with water and line the sieve with a double layer of the cheesecloth.
Pour the milk and cream into a medium stainless-steel or enameled pot, such as Le Creuset, and stir in the salt. Bring to a full rolling boil over medium heat, stirring occasionally. Turn off the heat and pour in the vinegar. Allow the mixture to stand for one minute, until it curdles. It will separate into thick parts (the curds) and milky parts (the whey).
Pour the mixture into the cheesecloth-lined sieve and allow it to drain into the bowl at room temperature for 20 minutes (for soft ricotta) to 25 minutes (for firmer ricotta), occasionally discarding the liquid that collects in the bowl. Transfer the ricotta to a bowl, discarding the cheesecloth and any remaining liquid. Use immediately or cover with plastic wrap and refrigerate.
The ricotta will keep, refrigerated, for 4 to 5 days.