Sprinkle the citric acid into an empty, large non-reactive stockpot. Pour in 1/4 cup water and stir it to dissolve, with the heat off.
Pour the milk into the citric acid solution and stir it to combine.
Turn the heat on and let the temperature rise to 90 degrees (use an instant read thermometer). You may see the milk is beginning to curdle, which is A-ok.
When the milk reaches 90 degrees, remove the pot from the burner and pour in the rennet mixed with water.
Give the mixture a gentle circular stir for about 30 seconds. Then use the spoon to stop the motion of the milk so it will “be still.”
Place the lid on the pot and walk away for five minutes. When you return after five minutes, the mixture will resemble a very soft custard.
With a long knife or offset spatula, cut the curd into a 1-inch checkerboard pattern, making lines across, then lines in the other direction like tick-tack-toe.
Return the pot to the the burner and stir it gently over medium heat until the temperature of the whey (the liquid that separates from the curd) reaches 105 degrees F.
Use a slotted spoon to transfer the curd to a colander set over a bowl. It will look stringy and wonderful.
Slowly spin around the colander once the curds are in to allow the whey to drain from the curd. Laugh as you go, it makes the food taste better.
Remove the cheese from the collander and gently squeeze it a few times to drain off more excess whey.That's mozzarella there friends!
Next, transfer the cheese to a microwave-save bowl and microwave the curd on high for 1 minute.
Remove the bowl from the microwave and pour off as much whey as you can. Pour the whey off into a bowl if you want, because you can make a high protein bread with it, or even scones! It's delicious stuff, why waste?
Press the curd together with your hands, give it a nice squeeze to get more whey out.
Microwave it again on high for 35 seconds, press the curd together again, and drain some more whey. The idea is that the more whey you get out, the more dense the cheese will be and the longer it will store in the refrigerator... but it may not last to the refrigerator because you may eat it all while it's still on the counter.
Next you stretch! Knead and stretch the curd a bit to drain more whey, then microwave it one last time for 35 seconds.
Knead in the salt and roll it into a neat ball.
And second to last, set the ball into an ice water bath and let it rest in there until totally cool.
Plate, top with your favorite seasonings, and enjoy!