Rinse the chicken livers under running water and put them in a saucepan with the other chopped ingredients: onion, carrot, celery, capers, sage, rosemary and butter.
There are not strict quantities to be followed when doing this chicken liver spread: just use all the ingredients equally, so that there are no vegetables prevailing over others.
Season the livers with salt. Use a very tiny pinch of salt, because the real flavour comes from the anchovy paste that you will add at the very end.
Stir frequently and cook for about 35 minutes, adding some tablespoons of water every so often. The livers should remain soft and wet. When the chicken livers are done, put all the ingredients in a food processor or use a mill to make a pâté.
This sauce is good when it is quite rough, not too velvety. It should keep its rustic character.
At the very end, gradually add some anchovy paste and cream with some butter, tasting every time to find the right level of saltiness.
You can make this one day ahead, and when it’s time to serve it just heat the chicken liver spread with some butter or chicken broth.