Grease a 10x12 inch rimmed baking pan and line the base with parchment paper, extending the paper 2 inches above the long sides.

Melt the white chocolate in a small heatproof bowl over a hot water bath, stirring until smooth.

Stir in the smooth peanut butter into the melted white chocolate until well combined.

Set aside the white chocolate-peanut butter mixture.

Melt the semi-sweet chocolate in a separate small heatproof bowl over a hot water bath, stirring until smooth.

Let the melted dark chocolate cool for 5 minutes.

Drop alternate tablespoonfuls of the white chocolate-peanut butter mixture and the dark chocolate into the prepared pan.

Gently shake the pan to level the mixture.

Pull a skewer through the mixture several times to create a marbled effect.

Let the chocolate stand at room temperature for 2 hours, or until completely set.

Using 2 inch cookie cutters, cut out flower shapes from the set chocolate.

Store the chocolate flowers in a single layer in the refrigerator.