MAKE IT NOW
You will need a gallon of whole milk and ½ cup heavy cream that’s not ultra-pasteurized, 2 teaspoons citric acid, and ¼ teaspoon liquid animal rennet. Citric acid and animal rennet can be mail ordered or bought from some cheesemongers; I used animal rennet (as opposed to vegetable) because I've found it produces more consistent results. Once you've gathered your ingredients, dissolve the citric acid in water. Then add the solution to the pot of milk and cream and stir very well. This is important. Stir for at least 30 seconds. Time it on your watch if you have to. The solution must be well incorporated.
Heat the mixture over medium heat to 90 degrees, stirring frequently to make sure the citric acid stays distributed. The mixture will begin to curdle and look slightly grainy with small lumps. This is normal and good.
Dilute the rennet in ¼ cup of cool water. Remove the pot from the heat. Stir the rennet mixture into the pot. Again, stirring here is very important. Stir for exactly 30 seconds to make sure everything is well combined. Then, no more stirring. Cover the pot and let it sit, undisturbed for 10 minutes. No peeking; magic is happening in there.
When the 10 minutes are up, remove the lid and check your curd formation (sounds fancy, like a real cheesemaker, right?). You should be able to gently pull the curd from the side of the pan to reveal clear whey. If you don’t have this, and your whey still looks milky, don’t panic. Simply cover, let the mixture sit for five more minutes, and then check again.
If you have a clean break, it is time to cut the curd. Using a flat metal spatula or a chef’s knife, being careful not scratch the sides and bottom of the pan, cut the curd into 1-inch blocks. Gently twist the pot using the handles on either side to jostle the curds and release them from the pot’s sides, then let it rest for a couple minutes, until the curds start to separate from each other. Then heat the whey to 105 to 107 degrees over low heat, turning and shifting the pot to heat it evenly. It should take about 10 minutes to get up to temperature.
Once the curd reaches 105 to 107 degrees, let it rest another two or three minutes. Then it’s time to remove it from the pot. First, place a colander in a large bowl. This will catch the whey, which you will use to stretch the cheese. Using a slotted spoon, gently remove the curd from the pan and transfer it to the colander. It will look like very loose pudding. Some pieces will fall apart. This is normal.
The curd in the colander will resemble a blob. See above.
Now it’s time to press out the remaining whey. This is one of the places that can make or break the cheese. There is no rushing this step (unless you want some accidental ricotta on your hands). Gently press from the top down to remove whey. If the cheese is pressing through the holes in your colander, you’re pushing too hard.
Swirl and gently press the curd around the colander until it becomes a cohesive mass and you can no longer see pockets of whey.
Take the drained whey and combine it with what’s left in the pot, then place the ball of curds on a cutting board; it should look about like medium-firm tofu and should be firm enough to stay intact in your hand. cut the curds into 1-inch chunks and place half of them in a deep, large heatproof bowl.
After removing all of the curd your water will probably look like this. You’re going to heat this liquid to stretch your cheese and if you leave all these floaty bits in there, they will coagulate and ruin your cheese. So strain the whey into a bowl, give the empty pot a rinse, then return the clean whey to the pot.
Add 12 cups water and 6 tablespoons kosher salt, then heat the mixture to 180 degrees. This hot liquid is what you are going to use to stretch the cheese. The salt will flavor it.
Put on a double layer of kitchen gloves (you’ll find out why momentarily). Pour half of the hot whey mixture over the curds you put in the bowl; the whey should cover the curds by at least 4 inches. At this point the curds will be much too hot to touch, so start by using a rubber spatula or two to gently bring the curds together and press them against the sides of the bowl to begin melting them.
As soon as humanly possible, dive in with your hands and gently stretch the curds out then fold the mass back onto itself, repeating until the curds are pliable and stretchy. A few tips: Keep the cheese submerged as much as possible to keep it hot, and work as quickly as possible. Keep the curds all in one mass for efficiency. If the cheese starts breaking apart instead of stretching, let it sit under the hot whey for 30 seconds or so to heat back up. Finally, be sure you’re stretching the cheese and not kneading it, or else you will end up with dense, chewy cheese. Think taffy, not bread.
Working quickly, form the mozzarella into balls. Take a small piece of cheese off the end of what you just finished stretching and stretch it around your thumb into a smooth, taut ball, then pinch it together at the bottom. Repeat, placing the balls in a clean bowl filled with cold water, until you’ve gone through all the cheese. Discard the stretching liquid, reheat the remaining whey mixture, and stretch and shape your second batch in the same way. working in two batches makes the stretching easier since the stretching liquid will stay warm and you have fewer curds to work with.
Eat it immediately, like I do, or wrap the mozzarella balls individually in plastic wrap. The cheese will stay fresh for up to 3 days.