Veal liver is difficult to find. In 2018, Wegman's in Allentown carried it. Last year Jan found some at Walmart, believe it or not... If veal liver is unavailable, go for baby beef, resorting to plain beef liver as a last resort. The liver varieties increase in "strength" in the order I listed them. Traditionally, chicken livers were used. I can't remember if I ever tried using them, but my mother always said they were too "rich" in flavor.
Devein liver, but don't go overboard if using the sieve method below. Season with salt and pepper to taste.
Oil is used loosely in the ingredient list. Some use chicken fat; I usually use coconut oil (refined). I would not use an oil with flavor such as olive oil, nor one with a low smoke point.
Heat oil over medium high heat. Add some of the liver and sautÃ© on both sides till cooked through (not red when sliced through). Repeat with remaining liver adding oil as needed.
After the liver, without cleaning the pan, add the onions and some more oil as needed. Sprinkle the onions with a little salt to help them release their water. Stir frequently scraping up any fond. Continue cooking until all water is given up and onions are very soft. We're not looking to brown the onions, but no problem if they do. Color will be difficult to determine due to liver fond. Remove onions and reserve.
While pan remains on the heat, add the port and deglaze the pan. Scrape up all remaining brown bits and reduce port to near syrup consistency.
Process liver, eggs, onions and port reduction in a blender or food processor until uniform.
To obtain a really smooth texture and remove any remaining vein particles, press chopped liver through a sieve.