Once you make fresh ricotta, you won't want to purchase it from the market again. Dante de Magistris gets goat's milk directly from dairies in Vermont, but you can find local brands at Whole Foods and many farmers' markets. It's important to set up the colander before you get started; once the milk reaches the right temperature, you don't want to keep cooking it.
2 quarts goat's milk
1 pint half & half
1/4 cup lemon juice
2 teaspoons salt
Rinse a 2-foot-long piece of cheesecloth with cold water. Fold it into four layers and line a wide-mouth colander with it. Set the colander in a large pan and place in the sink.
Clip a thermometer to the side of a large saucepan. In the pan over high heat, combine the goat's milk, half & half, lemon juice, and salt, stirring frequently and scraping the bottom to prevent scorching. When the mixture reaches 140°, stop stirring, but continue scraping the bottom of the pan to release any stuck curds.
When the mixture reaches 175° to 180°, curds and whey will separate. (The whey is the cloudy fluid settled at the bottom under the thick curds.) Remove pan from heat. Working from the side of the pan with a slotted spoon, gently ladle whey into the prepared colander. Lift the sides of the cloth to let the liquid drain. When the draining slows, gather the edges of cloth, tie them to create a bag, and hang from the faucet. Drain until the dripping stops, about 20 minutes. Untie the bag and pack ricotta into airtight containers. Use within one week.