Favorite kind that I make!
Traditional chocolate fudge relies on precise crystallization control for its grain, but this butterscotch variation utilizes marshmallow creme to interfere with sucrose structure. Stir the brown sugar, cream, butter, and creme in a heavy three-quart saucepan over medium heat. Bring the mass to a full, rolling boil. Maintain this boil for exactly six minutes while stirring constantly. Inadequate boiling leaves excess moisture, resulting in a soft, sticky paste that fails to set. Conversely, overshooting the time creates hard candy.
Remove the pan from the heat immediately after the timer expires. Add the butterscotch chips and stir until they melt completely into the hot base. Fold in the chopped Heath bars last. The toffee pieces retain their structural integrity and will not melt fully, which provides a contrasting crunch against the smooth interior. Pour the mixture into a buttered nine-inch square pan and chill until completely firm. Pair dense portions with bitter black coffee or unsalted roasted nuts to balance the intense sweetness.