Berakhot 36A

דכולהו שלקי.

in which all boiled vegetables were boiled. A certain amount of oil is added to anigeron.

אם כן, הוה ליה אניגרון עיקר ושמן טפל, ותנן, זה הכלל: כל שהוא עיקר ועמו טפלה, מברך על העיקר ופוטר את הטפלה!

However, if so, here too, anigeron is primary and oil is secondary, and we learned in a Mishnah: This is the principle: Any food that is primary, and it is eaten with food that is secondary, one recites a blessing over the primary food, and that blessing exempts the secondary from the requirement to recite a blessing before eating it. One need recite a blessing only over the anigeron.

הכא במאי עסקינן ⁠— בחושש בגרונו. דתניא: החושש בגרונו לא יערענו בשמן תחלה בשבת, אבל נותן שמן הרבה לתוך אניגרון ובולע.

The Talmud reconciles: With what are we dealing here? With one who has a sore throat, which he is treating with oil. As it was taught in a baraita: One who has a sore throat should not, ab initio, gargle oil on Shabbat for medicinal purposes, as doing so would violate the decree prohibiting the use of medicine on Shabbat. However, he may, even ab initio, add a large amount of oil to the anigeron and swallow it. Since it is common practice to swallow oil either alone or with a secondary ingredient like anigeron for medicinal purposes, in this case one recites: Who creates fruit of the tree.

פשיטא! מהו דתימא: כיון דלרפואה קא מכוין לא לבריך עליה כלל, קא משמע לן כיון דאית ליה הנאה מיניה, בעי ברוכי.

The Talmud challenges: This is obvious that one must recite a blessing. The Talmud responds: Lest you say: Since he intends to use it for medicinal purposes, let him not recite a blessing over it at all, as one does not recite a blessing before taking medicine. Therefore, it teaches us that, since he derived pleasure from it, he must recite a blessing over it.