Put the American Heritage chocolate and butter in a microwave safe bowl and microwave until melted, stirring every 30 seconds.
Let the chocolate mixture cool for 10 minutes.
Preheat the oven to 350 F.
Stir in the eggs, vanilla and sugar until the mixture is well combined.
Sprinkle the flour, baking powder and salt on top and fold together until just mixed.
Pour the batter into a 5" cast iron skillet.
Microwave the peanut butter for about 30 seconds to melt it. Then pour it on top of the chocolate batter. Use a knife to swirl the peanut butter into the batter.