In a large saute pan over low heat, melt the butter and cook onion, apple, and thyme, covered, until apples soften. Remove lid and increase heat to medium add the livers and cook until firm and still pink inside. Remove from the heat and allow to cool. Add the pepper, salt, and brandy and puree in a food processor; then chill, covered. Meanwhile whip the heavy cream to medium peaks. Fold into cooled, pureed liver mixture. Serve chilled.