in a large pot, combine citric acid with ¼ cup water and stir until dissolved.
Add gallon of milk, stir, heat to 90°F using an instant read thermometer; remove pot from heat.
Stir rennet into water until dissolved.
When the milk and citric acid have reached 90°F degrees (use an instant read thermometer) remove from heat, stir in dissolved rennet until combined, and place a lid on it for 10 minutes. Do not touch or move or remove lid during this time.
After the milk has become coagulated, cut a criss-cross-like pattern/grid pattern through the pot, using a knife or an offset spatula, reaching all the way to the bottom of the pan.
Return the pan to the burner, and heat to 105-106°F degrees, only barely stirring to disperse heat, and not break up curds. Use an instant read thermometer to determine when the mixture has reached 105°-106°F degrees.
Using a large slotted spoon, or hand held strainer, transfer the curds to a fine mesh strainer or colander to drain. Or pour them over three layers of cheese cloth over a large bowl to catch liquid whey.
Gather the strained curds into a smaller, microwave safe bowl and microwave for 15-20 seconds at 50% power, kneading, folding, stretching, and pouring off excess whey in between burst until internal temperature of curds reach 135°F with an instant thermometer.
Once cheese becomes smooth and shiny, tuck it into a little ball, pinching it neatly underneath itself.
Drop it into an ice bath for 5 minutes (optional).