You will need
Wash and trim chicken livers.
Heat oil in a frying pan and fry onion gently for about 5 minutes until soft but not coloured.
Add livers and one sprig rosemary. Cook gently, stirring occasionally, for about 8 minutes until livers are cooked through.
Add wine and simmer for 2-3 minutes. Discard sprig of rosemary.
Transfer to a blender and blitz for a few seconds until smooth.
Return purée to frying pan. Add anchovies, capers and stock and cook gently for 2-3 minutes. Season with a little salt and plenty of black pepper.
Stir in butter, a knob at a time. Keep pâté warm. If it separates, re-blend.
Garnish with remaining rosemary.