Add a little more schmaltz to the pan, increase the heat to high, and sauté the livers, salting them as you do, until they are warm all through with just some pinkness remaining, 7 to 10 minutes.
Peel the eggs. Run the onions, liver and eggs through a meat grinder fitted with a small die into a mixing bowl. Add 1 teaspoon salt, the pepper, and the vinegar, if using, and stir to combine. Stir in 1/2 cup of the schmaltz, in addition to the gribenes, if using (you can also wait and sprinkle them on top as a garnish), and continue to stir until all the ingredients are well incorporated. (As noted, this can also be done using a food processor.) Taste it and add more schmaltz, salt, vinegar, and pepper as you wish. Chill completely.
Nutrition information per 2 tablespoons:
Calories133Fat12 gSodium140 mg
Carbohydrates1 gSaturated fat4 gCalcium9 mg
Protein6 gCholesterol140 mgDietary fiber0 g