Heya read this after I sent the previous message...
Glad the 4 survivors are doing well!
They and Loreena are lucky to be in your care.
be well - Pip
I see what you mean, now; marbling is a situation with which I had not thought to deal.
Perhaps piercing the tongue with one of those needle type tenderizers or pre-slicing before cooking? This would open up the fat deposits and allow more to cook out.
...hmm, more thought needed.
Good evening;
What you may want to do is cook the tongue a day ahead of time, let it cool in the refrigerator, the fat rises and solidifies, scrape it off the top of the broth.
I do this to "de-fat" chicken and beef broth.
take care - Pip