Commentary for Chullin 222:11

"The law is: fish that were brought up in a fleishig dish are permitted to eat with milk spread." If the dish and the fish were [both] cold, it would never need to decide this, for there is no one who disagrees [in that case]. Rather, one of them must be hot, for regardless whether [one thinks that] the upper is stronger or the lower is stronger, it requires the removal of a layer, as we say in Keitzad Tzolin, when it cools it will absorb. [A case that plays out a nafka minah between Rashi's two explanations of the radish case on 112a:] In the name of Rashi, Rabbenu Yehudah ben Natan (Rivan) his son-in-law explained: "It is specifically "bringing up" that is permitted, but if the [fish] were cooked [in a fleishig dish]—it would be forbidden [to eat with milk spread], for it is considered one flavour." And a case came before him about eggs that were cooked in a milchig pot and he forbade to make from them a stuffing for meat. It is possible to bring evidence for his words from the radish that was cut with a knife [that was just used to cut meat] that it is forbidden to eat with milk spread, [for the first explanation of Rashi is:] "Because of its sharpness [in flavour], it absorbs more and becomes like one flavour", and it can't be that cooking is less powerful [at transferring flavour] than a radish! But according to the other explanation of Rashi, that the reason that it is forbidden is "because of the congealed fat on the knife which is not recognisable, and this would be primary flavour [transfer] to the radish" there would be no way to prove [the Rivan's case, since for his eggs there is no actual milk, unlike for the radish knife. [A new thing we can learn from another of Rashi's comments:] From the language of Rashi it implies that there is no difference between "bringing up" and "cooking" [for the fish in the dish], since above about Notein Ta'am bar Notein Ta'am, Rashi says: "If they were cooked with actual meat, or to eat milk in the dish, Shmuel would agree that it's forbidden, for it is transferring primary taste"—his explanation implies that it is cooking with the meat that would be forbidden, but cooking in the fleishig pot would be permitted!