It's just a thicker than usual brown beef based gravy. You should be able
to thicken up some regular jarred gravy with a little extra cornstarch to
match it. Jarred mentioned only for ease as you need just a ts (seems
low, sure it's not TB?).

Humm, others are comming up with maggi seasoning. They could be right, just
not the same thing I'm used to seeing as 'brown gravy'.