Curdling Milk with Juice Extracted from Rennet Skin

Description

The Chasam Sofer permits a poor Torah scholar to curdle milk using liquid extracted from a rennet skin (or hakeivah), relying on a double rabbinic leniency (trei derabanan): the extracted liquid without cooking is not Torah-level meat for basar bechalav purposes, and soaking rather than cooking is itself only rabbinically prohibited. He recommends also adding actual rennet to create zeh vezeh gorem, and requires periodic removal of the skin to prevent continuous soaking from reaching the halachic threshold of kavush.