Torah forbids eating the blood of an animal or bird. Therefore, it is necessary to extract the blood from the kosher slaughtered meat or liver.
With most meat, koshering consists of soaking the meat in water, salting it, and then rewashing it to remove the blood. With liver, this method of extraction is insufficient. Since liver contains such a large concentration of blood, the technique used for kashering liver is a special broiling process.
Washing: Thoroughly wash off all outside blood and remove all visible blood clots.
Broiling: When broiling a whole calf or beef liver, cut into it across its length and width before broiling. Then the liver should be placed with the cut side down on the rack for broiling. Immediately before broiling, salt all sides of the liver lightly with coarse salt.
Broil over an open fire with nothing between the fire and the liver so that the blood can flow out freely. A thin wire net with large holes maybe used to hold the liver over the fire. The liver should be rotated over the fire a few times so that all sides are exposed to the fire. The meat is to be broiled until the entire piece is at least half-done, not just the crust. The pieces of liver should not be too large for the heat to penetrate.
When broiling liver using an open flame from a gas range, stove top or under flame in broiler, cover all sides around the flame very well with foil so that no blood splashes onto the stove and renders it unkosher.
For the same reason, liver should not come into contact with kosher utensils such as plates, bowls, and knives, until it is completely koshered. The drippings and pan used to catch the drippings are non-kosher, and care should therefore be taken that kosher food does not come in contact with the non-kosher drippings or pan.
Rinsing: After broiling, the liver should be rinsed three times.
After removing the liver from the grate/wire net, the grate should then be left on the open flame for a few minutes to Kasher the grate.