2,302. Non-Jewish Butter

Maachalos Assuros 3:15

If a person eats non-Jewish cheese or milk that was milked by a non-Jew without a Jew watching, he is given stripes for acting rebelliously. As far as butter made by non-Jews, some Geonim permit it because the Sages didn’t issue a decree against butter. Other Geonim prohibit it because drops of milk might remain in it since the whey in butter isn’t mixed with the butter, which would nullify it because of its small volume. We are therefore concerned that the milk might be mixed with the milk of a non-kosher species.

Maachalos Assuros 3:16

The Rambam opines that if a person buys non-Jewish butter and cooks it until the drops of milk in it disappear, it is permitted. If you suggest that non-kosher milk was mixed with the butter and it was all cooked together, they were nullified because of their small volume. However, if the butter is cooked by the non-Jew, it is prohibited because of non-Jewish cooking, as will be discussed IY”H in chapter 17.