Combine 1 cup water with 1 ½ teaspoons citric acid in a bowl until dissolved.
In a separate bowl, combine ¼ cup water with ¼ teaspoon liquid rennet.
Pour 1 gallon whole milk into a large heavy pot. Stir in the citric acid mixture and heat over medium-high heat until it reaches 90°F on an instant-read thermometer.
Remove the pot from the heat, stir in the rennet mixture, and continue stirring for 30 seconds. Cover and set aside for 5 minutes.
After 5 minutes, use a long knife or large offset spatula to cut the curds in a crosshatch pattern.
Set the pot over medium heat and cook the curd mixture until it reaches 105°F. Set aside for another 5 minutes.
Separate the curds from the whey by using a fine-mesh sieve to drain off the whey.
Reheat the curds in hot water until they reach 135°F, folding and stretching them until smooth and elastic.
Shape the mozzarella into desired sizes and immerse in ice water for 5 minutes to set.
Enjoy the mozzarella in various dishes like Caprese salad, sandwiches, and pasta salad.
