Heat water on high heat to a simmer, whisk in the powders, then slowly whisk in the cheeses and cream cheese till emulsified.
Pour into a container and chill over night. The consistency when hot should be like hot molten cheese. When it chills it is like spreadable cheddar.
Grill the sandwich over medium-high heat with a shmear of mayo to give it a nice crust and to warm the cheese, which will give the sandwich a crunchy exterior with a molten interior.
Quicker and simpler basic grilled cheese blend: slice of American cheddar and smear of cream cheese.
Recipe originally published in JOY of KOSHER with Jamie Geller Magazine Shavuot 2014 SUBSCRIBE NOW