How to Cook Liver and Onions
To cook liver and onions, use a sharp knife to cut your beef or chicken livers into 1/2-inch thick slices. Next, dredge the liver slices in a mixture of flour, black pepper, and salt, so they're evenly coated. When you're finished, cook the liver slices in olive oil over medium-high heat for 2-4 minutes, flipping them over halfway through so both sides are browned. Finally, add chicken or beef broth and 2 sliced onions to the skillet and simmer everything for 15-20 minutes.
Discard the liver membranes if they haven't already been removed. Use your fingers to peel the thin, outer membrane off each liver. The membranes will come away easily. Try not to tear the liver as you remove the membranes. Liver is usually sold with the membranes already removed. Slice the livers into 1⁄2 in (1.3 cm) thick slices. Place 1 1/2 lb (680 g) of beef or chicken livers on a chopping board. Use a very sharp knife to slice the livers into strips. Be very careful when you use a knife to cut the liver thinly. Always make sure that you are using a sharp knife, as this is both safest and will make the best cuts.  into thin 1⁄4 in (0.64 cm) slices. Cut 2 onions Place the onions on a chopping board and use a sharp knife to cut the ends off. Slice each onion in half and peel the skin off. Place the flat surface of each onion on the chopping board and carefully slice each half thinly. Combine the flour, salt, and black pepper. Pour ½ cup (64 g) of flour, 1 tsp (2.3 g) of freshly ground black pepper, and ½ tsp (2.5 g) of salt into a bowl. Use a fork or whisk to mix the ingredients thoroughly. Season the flour with more or less black pepper and salt depending on what you prefer. Dredge the liver slices in the flour. Place each slice of liver into the bowl with the flour, black pepper, and salt. Turn each slice over in the bowl to make sure that all of the sides are coated with the seasoned flour. Gently shake each slice of liver as you take it out from the bowl to remove the excess. A light flour coating is all that is necessary. Heat the extra virgin olive oil in a large skillet for 1-2 minutes. Pour 3 US tbsp (44 ml) of extra virgin olive oil into a large skillet that has a lid. Adjust the temperature setting to medium-high. Brown the slices of liver in oil over a medium-high heat for 2-4 minutes. Place the slices of liver into the skillet. Make sure that the slices form only 1 layer and do not overlap. Let each side of the liver slices cook for 1-2 minutes and use kitchen tongs to turn them over after each side has browned. If all of the liver slices cannot fit into the skillet in 1 layer, brown them in batches instead. Place the first batch of the browned liver on a warmed plate while the subsequent batch cooks. Place the sliced onions to the skillet. Add the 2 sliced onions into the same skillet as the liver. Use a wooden spoon to occasionally stir the ingredients as they cook. If you cooked the liver in batches, add all of the liver back into the pan. Add the broth and simmer the ingredients for 15-20 minutes until a gravy forms. Pour 1 cup (240 ml) of beef or chicken broth into the skillet. Use a wooden spoon to combine the liver, onions, and broth. Reduce the heat to low and cover the skillet with a lid. Simmer the ingredients until the onions are tender and the broth has thickened. Use beef broth if you are cooking beef livers and chicken broth if you are cooking chicken livers. Check that the liver is cooked before removing the skillet from the heat. Use a knife to make a small cut into the thickest part of a piece of liver. The liver is ready when it looks very slightly pink in the middle with brown edges. If the liver looks raw or rare, continue cooking it for a few more minutes before checking it again. The liver tastes best when it is very slightly pink in the middle, as this means that it isn't overcooked. You can also check that the liver is cooked using a meat thermometer. Insert the probe into the thickest part of the liver and ensure that the temperature has reached at least 165 °F (74 °C). Serve the liver and place the sauteed onions on top of the slices. Use a spatula to divide the liver across 4 places. Place the onions and gravy on top of the liver and serve it immediately. You can also enjoy the liver with mashed potatoes for a hearty winter meal. Serve the mashed potatoes next to the liver and onions to help soak up the delicious sauce. Leftover liver and onions in the refrigerator for up to 3 days. Place the liver and onions in an airtight container and keep it in the refrigerator. 
Discard the liver membranes if they haven't already been removed. Slice the livers into 1⁄2 in (1.3 cm) thick slices.  into thin 1⁄4 in (0.64 cm) slices. Combine the flour, salt, and black pepper. Dredge the liver slices in the flour. Heat the extra virgin olive oil in a large skillet for 1-2 minutes. Brown the slices of liver in oil over a medium-high heat for 2-4 minutes. Place the sliced onions to the skillet. Add the broth and simmer the ingredients for 15-20 minutes until a gravy forms. Check that the liver is cooked before removing the skillet from the heat. Serve the liver and place the sauteed onions on top of the slices. 