Method

• 1.
  Line base and sides of a 22cm x 32cm shallow baking pan with baking paper. Melt chocolates separately in heatproof bowls over pans of simmering water (don't let bowls touch water). Stir until melted.
• 2.
  Pour dark chocolate into pan, then drizzle over milk chocolate. Use a skewer to swirl in a decorative pattern. Cool for 10 minutes, then chill for 30 minutes to set. Break into chunks to serve.