Heat milk in a sauce pot on medium-low heat until white whisps of steam begin to appear from the surface of the liquid.
Stir in sodium citrate with a whisk to dissolve and allow the milk mixture to scald (bubbles form around the outer surface and the edges begin to creep up the sides of the pan).
Turn off heat and begin to stir in cheese on small handful at a time, whisking until the cheese has fully melted. Repeat the process until all the cheese is incorporated. If the sauce begins to look clumpy, turn on a low flame under the pan to help incorporate the melted cheese.
