Line a fine-mesh or other tiny-holed strainer with a layer or two of cheesecloth and set it over a large bowl with enough clearance that the bottom of the strainer won’t touch the bowl once it has 4 cups of liquid in it, or the cheese won’t drain. In a heavy medium-large saucepan, heat the milk, cream, and salt over medium-high heat until just below a simmer — it will look like it’s foaming and register about 200 to 205 degrees F. Remove from heat. Stir in vinegar and wait 4 minutes, then pour it through the cheesecloth. Drain for 10 to 20 minutes; it will still look pretty wet but will barely be dripping from the strainer. The amount of time it takes to drain has to do with the size of your cheesecloth holes. Don’t worry if it drains too much, however; you can always add back some whey if it’s not the right consistency. Transfer the contents of the cheesecloth to a food processor or blender and blend until very smooth, a few minutes, scraping down as needed. That’s it — you made cream cheese! If it seems stiffer, you can add some whey back, 1 teaspoon at a time, blending it in. Save the whey for other good things, like a soup stock or as the water in a bread recipe. To make different variations of cream cheese, add the respective ingredients per cup of plain cream cheese.