Combine the milk and buttermilk in a large, heavy pot over high heat. Attach the candy thermometer to the side of pot and stir occasionally as the mixture heats. 8 cups 1% milk, 2 cups buttermilk
Line a colander with 3-4 layers of cheesecloth, allowing overhang, and place the colander in the sink.
When the mixture in the pot reaches about 140°F, small clumps (curds) will begin to form. Once this starts to happen, you will need to stir almost constantly from this point on.
At about 175°F to 180°F, the curds will separate from the liquid (whey) and float to the top. When this happens, remove from heat.
Using a skimmer or large slotted spoon, transfer the solid curds to the colander.
Gather the cheesecloth around the ricotta and lift. You want to drain some of the excess liquid without squeezing all of it out.
Return the cheese to the colander and let it rest for about 20 minutes at room temperature.
Transfer the cheese to a small bowl, removing the cheesecloth. Sprinkle with salt and mix gently.
Cover and chill until cold, at least 2 hours.