Karah prasad is made of equal parts by weight of wheat flour, sugar, ghee and water, cooked in an iron karahi while reciting, and distributed to everyone present at the end of a service.
The three ingredients and the method are fixed. It is offered in front of the Guru Granth Sahib Ji, touched with a kirpan, and then given out.
It is given to everyone in the same form, into the cupped hands, with no distinction of any kind, and refusing to receive it or receiving it separately would be a serious matter. Like the langar, it is a commensality rule enforced as ritual.
The requirement that everyone present receives it, including visitors of any religion, is explicit.
It is extremely rich, which is deliberate. It was designed for people doing physical work in a cold climate and it has not been adjusted since.
It is prepared in an iron karahi with the ardas said over it, and a kirpan is touched to it before it is given out.
Five portions are set aside for the Panj Piare before the rest is distributed, which is the same principle as the amrit and the same five.
Nobody is asked who they are before receiving it. That is the whole point and it is written into the rehat rather than left to practice.