Used more cheese than called for (14oz cheddar and 8oz American), just add more whole milk if the sauce gets too thick. Could also use some chicken stock for thinning, but that will alter the flavor profile.
Been looking forward to make this clone recipe since I had the real one at an anime con in Arizona called "UwUcon." Made 1 serving worth per the listed ingredients list. In the marinade I added a tablespoon of bourbon. Ran the marinade too long, probably should have been no more than an hour. Used "toast bread" from a local Asian market and the butteryness of it overpowered the meat despite onions and garlic from the marinade being cooked alongside it. Definitely use milk bread if possible. But the slices I used were too small (size plus thickness) and out of half a pound of marinaded beef I have 4 sandwiches potentially. The bread will 100% determine how much of the meat is used.