Pour the gallon of milk into a large pot
Bring to a boil over medium heat
Watch carefully, as it will boil over almost as soon as it starts to boil
As the milk begins to boil, pour the buttermilk into the pot in a steady stream while stirring constantly
The milk will separate into curd and water
Place a cheesecloth into a colander, and pour the milk mixture through it
Reserve some of the liquid for later
Let the milk mixture sit in the colander for a couple of hours, or until it stops dripping
After the curds are strained and settled, transfer them to a food processor
Process until smooth
It should be able to form a ball if it is the right consistency
If it is too dry, add a little of the reserved liquid and process again
The consistency should be like a firm ricotta cheese
Turn the cheese out onto a clean surface, and knead until smooth
Form into a ball, and wrap in plastic
Refrigerate until needed
To cook the paneer, heat the oil in a large heavy skillet over medium-high heat
Cut the paneer into bite size pieces
Fry for about 1 minute, or until a very pale golden brown
Drain on paper towels
Add to your favorite curry or dish