Rusk * Gravy is one of the many different rations available through CLMIL Rations, which are bagged rations handed out to Clavic military forces.
In the 2nd edition bags, Rusk * Gravy is meal 30.
Bag Details
Apart from the standard icons and instructions, the label says "Seasoned * Toasted Rusk * Gravy" and the item number is CLR8866344.