How to Make It
Melt butter in a large skillet over moderate heat; add onion and garlic, and sauté until onion is translucent, 7 to 8 minutes. Add chicken livers and thyme, and cook, shaking pan occasionally so livers cook evenly and onions do not brown, until livers are cooked through but still moist, about 5 minutes. Remove pan from heat; add Cognac, then return to heat, taking care to stand back in case of a flare-up. Simmer until mixture reaches a syrupy consistency, 4 to 5 minutes.
Transfer mixture to food processor, and pulse until finely chopped. With machine running, add cream, salt, and pepper, and process until smooth. Place in a small bowl and cool to room temperature. Cover tightly; chill until set, about 30 minutes.