Put the fat through a food grinder or into an electric blender. Turn into a large, heavy skillet. Add the butter and the flour with enough milk to make a mixture of thick porridge-like consistency. Let cook until the fat has absorbed. Cook very slowly. Skim off any fat which does not absorb.
Wash and clean the liver thoroughly. Cut it in manageable pieces and feed through the finest blade of your meat grinder. Mix with the fat mixtures and put through a coarse sieve to make a smooth paste.
Add the egg yolks, slat, pepper and a good pinch of the ground cloves.
Beat the egg whites until stiff and add.
If you wish, add a little grated onion to the blend.
Fill bread tins about ¾ full of mixture. Bake in a pan of hot water 1¼ hours, or until a knife inserted in the middle comes out clean. (Preheat oven to 325 degrees.) Do not remove any fat that may come to the surface; it will be absorbed.
Let cool in the pans and dip in boiling water to loosen after it has chilled overnight. Slice thin, serve on dark bread, imaginatively garnished.