In a spice grinder or clean coffee grinder, combine peppercorns, allspice, clove and coriander seeds; grind until fine and set aside.
Melt 2 tablespoons butter in a skillet over medium-high heat; when foam subsides, add onion and cook until softened, about 3 to 4 minutes. Add livers to pan and sprinkle with salt; cook livers on one side until they begin to brown, about 2 minutes, then flip them and cook the other side. Be sure to keep heat relatively high so that the outside of livers sears and inside stays pink.
Put onion, livers and their buttery juices into a food processor or blender with remaining butter, the cream, spices and brandy. Purée mixture until it is smooth; taste and adjust seasoning.
Put pâté in a terrine or bowl, smooth top and put in refrigerator for 2 to 3 hours or until fully set. Serve pâté with bread or crackers.