Place onion and apple in a food processor with the steel knife blade; process until coarsely chopped.
Melt 3 tablespoons butter in a large skillet over medium heat. Add onion and apple; cook and stir until lightly browned, 5 to 10 minutes. Return onion and apple to food processor.
Melt 5 tablespoons butter in the same skillet over high heat; cook chicken livers until browned and just done inside, about 5 minutes. Reduce heat to low and pour in brandy; allow to warm up without stirring. Carefully light the liquid; let flames subside.
Transfer chicken liver mixture to the food processor with onion and apple. Add cream and process until very smooth. Transfer mixture into a bowl and refrigerate until cool, at least 30 minutes.
Cut the softened 1/2 cup butter into pieces and process in the food processor; add about 1/3 of the liver mixture and blend about 5 seconds. Repeat 2 more times with remaining liver mixture. Add lemon juice, salt, and pepper and blend well.
Transfer pate to a serving dish or several small dishes; top with 1 tablespoon melted butter. Cover loosely with plastic wrap; refrigerate until chilled and set, about 3 hours.