Right, but the 2-3% is total of liquid plus cheese weight, correct?
Yes, that's correct. I've been following the Modernist Cuisine formula with fun and tasty results. They recommend 4% of the "liquid weight" for the amount of sodium citrate to add. That works out to roughly 2% of the "sum of liquid weight plus cheese weight." Almost
any cheese you like can be made into a smoothly melting cheese using only 3 ingredients: your cheese of choice, your liquid of choice, and a small amount of sodium citrate. The resulting flavor and smooth texture will be great.
For example, when making a smooth cheese sauce for Mac & Cheese, consider the weight of the cheese to be 100%, then they recommend the weight of the liquid should be 93% of the weight of the cheese, and the weight of the sodium citrate should be 4% of that liquid weight (which is approximately the same as 2% of the sum of the liquid weight plus cheese weight). The formula is very forgiving so there's no need to be extremely precise.
This method of making a silky and non-separating cheese sauce is very easy. No need to make a roux or a bechamel sauce which masks the pure flavor of your favorite cheese. Just whisk a teaspoon or two of sodium citrate into your liquid of choice, heat the liquid and blend in your favorite grated cheese with a stick blender, regular blender, or whisk. This results in a smooth, creamy texture that doesn't become grainy, greasy, or separated. You can also add in any flavors you enjoy like Rotel with green chile or Pico de Gallo.
You can refrigerate any leftovers and reheat it the next day to enjoy the smoothest cheese sauce ever!
For other types of cheese sauces, you can control the final "thickness" of the cheese sauce depending on your ratio of liquid to cheese. If you weigh your cheese and then measure the liquid (water, milk, beer, wine, stock, etc.) as a percentage of that cheese weight, you will get:
Cheese plus 0% to 35% liquid weight = firm, use for making "American" cheese slices for burgers, etc.
Cheese plus 35% to 85% liquid weight = thick and flowing cheese sauce, good for dips and queso.
Cheese plus 85% to 120% liquid weight = thin cheese sauce, good for fondues, mac & cheese, etc.
Cheese plus 120% liquid weight or more = continues to become a thinner and thinner sauce.
Caution: Sodium Citrate is NOT the same as Citric Acid. Use Sodium Citrate for the results above.