Coarsely chop the chocolate bar into small chunks and place them in an oven safe mixing bowl. Carefully melt the chocolate with microwave oven on high, stopping and checking every 10 seconds.
Add the remaining ingredients except peanut butter into the melted chocolate and use a spoon to mix them until smooth.
Place mini cupcake liners in a mini muffin pan. Spoon approximately 1-1/2 teaspoons of chocolate batter into each muffin cup. Making approximately 10-12 cups. Refrigerate the muffin pan until the chocolate is hard. Approximately 15 minutes.
Microwave the natural peanut butter for a few seconds until it is slightly runny. Spoon approximately 1 teaspoon peanut butter into the chilled chocolate cups. Refrigerate the muffin pan until the peanut butter layer is stiff.
Spoon the rest of chocolate batter into each muffin cup evenly. Refrigerate the muffin pan until the cups are hard.
Serve cold. These cups can be refrigerated in an airtight container at least one month.