And you can make sodium citrate at home with 4.9 grams of baking soda and 3.7 grams of citric acid. Add about 15 ml of water to start the reaction and wait. The cool thing about this reaction is that there shouldn't be any side products beyond some co2 and a little water.
Anyway, you'll get about 5 grams of sodium citrate dissolved in water. (and you can safely boil off the water to get pure sodium citrate powder)
Which is far more than you need to make a pot of melty goodness.
Now, you could just make a béchamel and slowly melt a young cheese into it, but that's never going to taste the same. Sodium citrate adds in just a little extra tartness, while also making the cheese so creamy that it's kind of hard to describe for those who've not had it.