Chullin 109 - The Udder
Since the Torah said, "You shall not cook a young goat in its mother's milk," only milk from an animal that is fit to be a mother and is alive falls under this prohibition. Still, the Sages prohibited cooking other meat in this milk. Nonetheless, the meat of the udder is different.
One should tear open the udder prior to cooking and extract its milk. If he did not tear it open and prepared it as is, he does not transgress on account of it. Rabbi Zeira said, "It is permitted to consume the udder prepared with its milk." But we just learned that "one does not transgress on account of it." This seemed to imply that it is prohibited by the Sages, only that one does not transgress the Torah!? Rabbi Zeira was talking about roasting, where the milk drips off, and the ruling - about boiling, where the milk gets out, becomes prohibited, then gets reabsorbed.
Yalta, the wife of Rav Nachman, said to him, "Whatever God forbade us, he allowed something similar. For example, there is a fish that tastes like pig, and one can marry a non-Jewish woman whom he captures in battle. I want to eat meat in milk." Rav Nachman asked his chefs to roast udders on a spit for her.
Art: Leo Malempre - Milking the Goat