Avodah Zarah 38A

אלא מדרבנן, וקרא אסמכתא בעלמא.

Rather, the cooking of non-Jews is prohibited by rabbinic law, and the verse is cited as a mere support.

אמר רב שמואל בר רב יצחק אמר רב: כל הנאכל כמות שהוא חי ⁠— אין בו משום בישולי גוים. בסורא מתנו הכי, בפומבדיתא מתנו הכי: אמר רב שמואל בר רב יצחק אמר רב: כל שאינו נאכל על שולחן מלכים ללפת בו את הפת ⁠— אין בו משום בישולי גוים.

The Talmud discusses the particulars of the prohibition against eating the cooking of non-Jews. Rav Shmuel bar Rav Yitzḥak says that Rav says: Any item that is eaten as it is, i.e., raw, is not subject to the prohibition against eating the cooking of non-Jews. The Talmud remarks: In the study hall in Sura, they taught it this way. In Pumbedita, they taught it like this: Rav Shmuel bar Rav Yitzḥak says that Rav says: Any item that is not eaten together with bread on the table of kings is not subject to the prohibition against eating the cooking of non-Jews. In other words, foods that are not eaten by distinguished individuals are not subject to this prohibition.

מאי בינייהו? איכא בינייהו: דגים קטנים, וארדי, ודייסא.

The Talmud asks: What is the practical difference between these two opinions? The practical difference between them is with regard to small fish, mushrooms, and porridge. These foods are not eaten raw, but they are not eaten by distinguished individuals. Consequently, these foods are prohibited according to the version taught in Sura, but permitted according to the version taught in Pumbedita.

אמר רב אסי אמר רב: דגים קטנים מלוחים אין בהן משום בישולי גוים. אמר רב יוסף: אם צלאן גוי סומך ישראל עליהם משום עירובי תבשילין, ואי עבדינהו גוי כסא דהרסנא ⁠— אסור.

Rav Asi says that Rav says: Small, salted fish are not subject to the prohibition of the cooking of non-Jews, because they can be eaten raw. Rav Yosef says: If a non-Jew roasted these fish, a Jew may rely upon them for use in the mitzva of a joining of cooked foods, which must be prepared in order to permit cooking for Shabbat on a Festival that occurs on a Friday. And if a non-Jew made them into kasa deharsena, a dish of fish fried in oil and flour, the dish is prohibited. In this case, since the flour had not been edible, it is considered the cooked food of a non-Jew.