This recipe comes from Saveur maganize and is the liver spread served at Katz's Delicatessen in NYC's Lower East Side. It is more of a pate or spread than a chopped liver, but what's in a name? Serve with rye bread.
The recipe does not call for it and of course it would not meet kosher requirements, but I always soak my liver in milk for an hour or two. I find that this really improves the taste of liver, especially beef liver.
Heat broiler to high, and place beef livers on an aluminum foil-lined baking sheet. Broil, turning once, until cooked through, about 10 minutes. Transfer to a food processor.
Place chicken livers on baking sheet and broil until cooked through, 8 to 10 minutes; Transfer to food processor.
Heat oil in a medium skillet over medium heat and add the onions. Cook, stirring often, until soft, 10 to 12 minutes. Transfer to food processor.
Add the remaining ingredients to the food processor and process until smooth.
Transfer to a medium bowl, cover with plastic film and chill.
Note: If you have a small food processor, cut the cooked beef liver into smaller pieces, quarter the eggs, mix with the chicken livers and all other ingredients in a large bowl, then process in batches.
Note2: I use butter, as I don't usually have schmaltz.