Beef liver is best cooked by first soaking it in milk for 30 minutes to an hour to mellow out the bitter flavor, then cooking it quickly at medium to medium-high heat to keep it tender and slightly pink inside. A popular method is to slice the liver approximately one inch thick, coat it lightly in flour seasoned with salt and pepper, and sauté it in butter or oil for around 3-4 minutes per side. Serve it with caramelized onions and optional mushrooms or gravy for added flavor. Here are a few key steps to cook beef liver well:

• Soak the liver in milk for 30 minutes to an hour and then pat dry.
• Lightly season and coat the liver slices in seasoned flour.
• Sauté onions in butter or oil until soft and caramelized and set aside.
• Cook the liver in butter or oil on medium heat for about 3-4 minutes per side until browned but still slightly pink inside for tenderness.
• Serve liver topped with the onions and optionally mushrooms or gravy.

This method helps achieve a balance where the liver is flavorful, tender, and not overly metallic or tough.