Responsa for Pesachim 80:17
ותניא נמי הכי אין נותנין קמח לתוך החרוסת ואם נתן ישרף מיד לתוך החרדל ר' מאיר אומר ישרף מיד וחכמים אומרים יאכל מיד אמר רב הונא בריה דרב יהודה אמר רב נחמן אמר שמואל הלכה כדברי חכמים א"ל רב נחמן בר יצחק לרב הונא בריה דרב יהודה
<big><b>GEMARA: </b></big>R'Kahana said: The controversy is [about putting flour] into mustard; but [if it was put] into haroseth, all agree that it must be burnt immediately. And it was taught likewise: Flour must not be put into haroseth, and if he did put [it], it must be burnt immediately. [If put] into mustard, - R'Meir said: It must be burnt immediately; but the Sages rule: It must be eaten immediately.<span class="x" onmousemove="('comment',' The greater strength of mustard retards fermentation, hence the controversy. But it ferments very quickly in haroseth.');"><sup>31</sup></span> R'Huna the son of Rab Judah said in R'Nahman's name in Samuel's name: The halachah is as the words of the Sages. Said R'Nahman B'Isaac to R'Huna the son of Rab Judah:
Teshuvot Maharam
A. In France such bread is not eaten by Jews; even the sale of such bread to a Gentile is prohibited, lest the latter resell it to a Jew. The reason for this is that a Jew is permitted to eat bread baked by Gentiles from flour belonging to Gentiles, but he is not permitted to eat bread baked by a Gentile from flour belonging to a Jew.
SOURCES: Pr. 33; L. 342. Cf. Mord. A. Z. 830; Hag. Maim., Maakalot Asurot 17, 90; Agudah A. Z. 29; Sefer Haparnes 93.
Teshuvot Maharam
A. This bread may not be eaten, lest perchance one eat it with milk. However, it may be sold to a Gentile, since in a Rabbinical prohibition we do not take into consideration the remote possibility that the Gentile will resell the bread to a Jew.
This Responsum is addressed to R. Tobiah.
SOURCES: Am I, 77.
Teshuvot Maharam
A. In France such bread is not eaten by Jews; even the sale of such bread to a Gentile is prohibited, lest the latter resell it to a Jew. The reason for this is that a Jew is permitted to eat bread baked by Gentiles from flour belonging to Gentiles, but he is not permitted to eat bread baked by a Gentile from flour belonging to a Jew.
SOURCES: Pr. 33; L. 342. Cf. Mord. A. Z. 830; Hag. Maim., Maakalot Asurot 17, 90; Agudah A. Z. 29; Sefer Haparnes 93.