Trim the chicken livers and remove any membrane, gristle, sinew, or greenish parts.
Heat olive oil and butter in a frying pan, then gently cook the shallots, onion, garlic, thyme, and spices until soft.
Add the chicken livers and cook until browned outside but slightly pink inside.
Pour in the brandy, sherry, or port and simmer briefly.
Transfer everything to a food processor with butter and double cream.
Blend until completely smooth, then pass through a fine sieve if desired.
Spoon into ramekins or a terrine and smooth the tops.
Seal with melted butter if preferred.
Chill for at least 4 hours or overnight before serving.