Add brown sugar, oil, 1/2 cup butter, and 1/2 cup reserved chocolate mixture and beat on medium speed until flour is evenly distributed and mixture is smooth, about 2 minutes. (bonappetit.com)
Sprinkle reserved chocolate and mixed rosemary evenly over the top of the cake batter. (micheleagarcia.com)
Pour reserved chocolate mixture (it should be the consistency of fudge sauce) over center of peanut disk. (epicurious.com)