i have read that soup and gravy made from meat are forbidden on days of complete abstinence, although i can’t find any official references online(although some random Catholic sites says it’s okay, but give no reference), but out of one of my more current Catholic encyclopedia’s it defines penitential abstinence as - *"Depriving oneself of meat or foods prepared with meat (sauces, gravies, soups from meat stock) on days prescribed by the church as “penitential”. *
and out of another Catholic encyclopedia, although less recent - “refraining from eating the meat from mammals or fowl, and soup or gravy made from them.”
and out of “My Catholic Faith” by Bishop Louis Laravoire, which is the newer “ecumenical spirit edition” says - “On days of complete abstinence meat, and soup or gravy made from meat, may not be used at all”
and then several other of my Catholic dictionary/encyclopedias say the same,
i’ve seen several sites, as i said, which claim it’s okay, but don’t trust it just cause it’s a catholic site, you have to get the answers from the church, either ask your priest or bishop(although sometimes even the priest doesn’t know), or do as i did, check it out in a church approved catholic dictionary or encyclopedia,
it’s true, there can be exemptions made by our bishops, but you don’t see that very often, and so you can’t just assume it’s okay, you either have to find out, or just don’t eat it.