A savvy home cook knows the best approach to cooking liver in the oven depends on the type and age of the liver. Poultry livers, calf livers and livers from other young animals are tender with mild flavor; these hold up to the dry heat of baking. Beef and other adult livers, however, are tougher with a potent flavor. They do better with a wet heat cooking method like braising, which provides good opportunity to temper and balance the liver's taste. Choose a suitable technique to more thoroughly enjoy this adventurous and nutritious alternative to steak and other more common animal proteins.
Preheat the oven to 375 degrees Fahrenheit for about 20 minutes. Lay a sheet of aluminum foil over a baking tray and grease it with a little bit of cooking oil.
Wash the liver under cold running water and blot it dry with clean paper towels. Cut the liver into slices anywhere from 1/2 to 2 inches thick, as you prefer, with a sharp knife. Because liver must be cooked to well done -- 160 degrees Fahrenheit -- to be safe, slicing it into thinner pieces prevents the outside from cooking too quickly.
Pat the liver slices with plenty of salt and pepper, as well as other complementary herbs and spices. For example, some combination of thyme, rosemary, basil and tarragon works nicely; curry or chili powder add heat; and a beef rub is an easy way to impart depth of flavor.
Space the liver pieces out on the lined baking tray and put the tray into the middle of the oven. Bake them for 20 to 30 minutes, until they reach an internal temperature of 160 F. Insert an instant-read thermometer into the center of the liver to determine doneness.
Preheat the oven to 325 F for about 15 to 20 minutes. As it heats, rinse the liver and pat it dry with paper towels. Cut the liver into 1- to 3-inch slices, as you prefer, with a sharp knife. Season the pieces liberally with salt and pepper, along with any other herbs or spices you'd like to use.
Put a Dutch oven over medium-high heat on the stove and coat the bottom with cooking oil. Let it become shimmering hot. Drop the liver slices in and sear them for about 3 minutes, turning the pieces frequently to cook all sides. Remove the liver to a plate.
Pour a braising liquid into the Dutch oven, using less than would completely submerse the liver when it goes back in. Wine, beer and broth work well. Rub the tip of a spatula or cooking spoon over the bottom of the dish to release the caramelized remnants from searing. Season the liquid with any desired aromatics, herbs and spices. For example, include chopped carrots, celery, onion, garlic, shallot, leek, scallion, ginger, rosemary, basil, tarragon, thyme, soy sauce or citrus zest.
Place the liver strips back in the Dutch oven and bring the liquid to a boil. Put the cover on the pot and put it into the oven. Braise the liver for 20 to 30 minutes, depending on the thickness of the liver slices, until they're fork-tender and cooked to 160 F as measured with an instant-read thermometer.