Heat chicken fat or vegetable oil in sauté pan over medium heat for 1 minute, and sauté onion in it 20 to 25 minutes, or until very soft and lightly golden. add uncooked liver, and cook until just pink inside, a few minutes.
Place onions and liver in food processor with eggs, brandy and starch, and process until smooth. Season to taste with salt and pepper.
Arrange bay leaves shiny side down in loaf pan, and spoon liver mixture on top, pressing gently with spoon to get rid of any air bubbles. Set pan in a larger pan two-thirds filled with warm water, and bake 20 minutes. Cool, and unmold. Serve with rye bread.