Place smoked fish in a small pan. Pour on water to cover. Bring to boiling, reduce heat. Cover and simmer until fish flakes easily, 15-20 minutes. Let fish cool in cooking liquid. Drain, separate fish into flakes, discarding any bones. Place fish, lemon juice and thyme in food processor or blender container. Cover and blend until smooth. Add butter in a slow, steady stream, pureeing until mixture is smooth. Whip cream until stiff. Fold in fish mixture until well combined. Add pepper to taste. Cover and refrigerate to blend flavors, several hours or overnight. Remove from refrigerator about 30 minutes before serving. Garnish with parsley and olive slices. Serve as a spread for toasted French bread.