Fry the chopped onions until golden.
Rinse the chicken livers, put into a saucepan and cover with water. Bring to the boil and drain straightaway. Cover again with fresh water and bring to the boil. Skim off any scum the forms on the surface of the water. Add salt and simmer for 15 minutes. Chicken livers are tender and cook quickly.
Drain and while still hot put the chicken livers in a food processor (or mincer) and blend. Add the chopped hard boiled egg, cooked carrot and fried onions and blend again. are minced. Add salt, pepper and butter, according to taste, and blend into a smooth paste.
Set the pâté aside for 20 to 30 minutes to allow it to solidify slightly.
Spread a long rectangle of pâté 0.5 cm thick over a sheet of greaseproof or wax paper. Spread a layer of butter on top of the pâté.
Roll into a Swiss roll. Cover the pâté with greasproof paper and place in the fridge.