Cutting beef liver into strips before cooking helps it cook more quickly. Additionally, it exposes more area to any marinade you use on it before cooking. If you are cooking for people who might not like the idea of eating beef liver, cutting it into strips can make it easier to disguise what you are cooking. You can then saute it with onions, in the classic style, or try other quick-cooking methods such as stir frying it.
Place a damp towel on the counter, where you will be putting your cutting board. Make sure the towel is flat, with no creases or bunches.
Lay the cutting board directly on top of the damp towel so that the long side is perpendicular to you. Press it into the towel so that the dampness of the fabric locks it into place and keeps it from slipping as you cut.
Place the beef liver in the center of the cutting board with the long side of the liver parallel to the long sides of the cutting board.
Hold the knife at the bolster, where the blade meets the handle. Grip it firmly, but not so tightly that your knuckles go white. Place the tip of the knife on the board above where you want to cut the liver.
Begin cutting the liver on the bias—diagonally—into half-inch wide strips. Draw the tip of the knife back toward you as you cut, rocking the blade on the cutting board toward the bolster. Use the knife tip to guide your cut line, always keeping it in contact with the cutting board.
Raw beef liver will be bloody. If possible, choose a cutting board that has a gutter around the edge to collect the juices. You can reserve them for a pan sauce or discard them.
If your raw beef liver is slightly frozen, cutting cleanly will be even easier. Do not attempt to cut completely frozen beef liver, however, as it will be very difficult or impossible to get your knife through.