SC - Chocolate documentation?

[Bronwynmgn at aol.com]

In a message dated 4/29/2000 10:48:23 PM Eastern Daylight Time, 
rygbee at montana.com writes:

<< Modern merchants sell Carob as an equivalent-substitute for Chocolate.
 
 Therefore, Chocolate = Carob
 
 Carob is demonstrably period, also called Manna or Saint John's Bread
 [for the early summertime ripening of the sweet pods].
 
 Therefore, we can call Chocolate "Mock Saint John's Bread" and eat it
 too. >>

The only place I have seen this claim made is in Fabulous Feasts.  Do we have 
any evidence for the use of Carob, St John's Bread , or Manna (or the 
equation of carob with the other two names) in the middle ages other than Fab 
Feasts?

Brangwayna Morgan