The cooking time for the liver varies depending on the size of the liver and the method of preparation. For example, if you are pan-frying small pieces of liver, it can take as little as two to three minutes per side. If you are baking or roasting larger pieces of liver, it can take 20 to 30 minutes in an oven preheated to 350 °F (177 °C). Ensure to check for doneness by inserting a thermometer into the thicker part; when it reaches an internal temperature of 145°F (63°C), your liver is done. Let it rest for 3-5 minutes before serving. Always check with a food thermometer to ensure that your meat is cooked properly and safely!