זָכוֹר אֶת יוֹם הַשַּׁבָּת לְקַדְּשׁוֹ… לֹא תַעֲשֶׂה כָל מְלָאכָה
“Remember the Sabbath day to keep it holy… You shall not do any melakha (labor).” (Shemot 20:8)
Is there a permissible way to make fresh pour-over coffee on Shabbat?
There are two possible concerns in this case, both of a serious d’oraitta nature. One is bishul, cooking. Does the pouring of hot, yad soledet bo water over the ground coffee beans constitute an act of cooking them? The second is borer, selecting. Once the water is poured over the coffee beans and creates sludge (the technical term), the flavored water is then selected out of the mixture through the filter, which would seem to be a classic case of borer with a utensil that is made for selecting, a d’oraitta melakha. Let us examine both of those.
As to bishul – There is some question as to whether bishul would apply to roasted coffee beans: Some would posit that it should be exempted because of the principle that ayn bishul achar bishul, that once something is cooked, it is not a Shabbat violation to cook it again. Others argue against this for multiple reasons, chief among that the that principle only applies when the item was previously cooked, and here the coffee beans were not cooked, but roasted.
The solution to the problem of bishul, however, is obvious. Just use a kli shelishi and you are fine. This means, pouring water from the urn into a cup, from that cup into another cup, and pour from the second cup onto the coffee beans. This is no different from the use of tea bags in a kli shelishi on Shabbat (some even permit their use in a kli sheni, although this is not my practice). For those who don’t use tea bags, out of concern that the tea leaves will always cook in boiling water, regardless of the kli, then they would similarly not be able to pour the hot water over the coffee beans. (One could argue that it would even be permissible to pour from a kli sheni onto the coffee beans, but I would prefer to be strict regarding that).
As to the problem of borer – surprisingly, in this case, this is not a halakhic concern because of the way the process takes place. What happens here is that you pour water onto the grounds, the water mixes with the grounds and gets flavored by them, and then the water comes out through the filter into the cup. You never took something that was a mixture and removed from it the part that you wanted. You didn’t shake or manipulate the filter with the sludge in it or do anything to the sludge itself. It was water in, (flavored) water out.
While this is a little shocking, it is actually a case in Shulkhan Arukh regarding pouring water onto lees in a filter, and having grape-flavored water come out, which is permitted. See SA OH 319:3, MB 33, and Shmirat Shabbat 3:58. In the end, this is not much different than what we do with a tea bag, which is really nothing more than ground tea leaves inside a filter which is containing them. Just make sure to not shake the coffee filter and, in the case of tea, to not shake the water out of the tea bag.