Method

• 1.
  Begin this recipe 1 day ahead.
• 2.
  Place the white chocolate in a heatproof bowl over a pan of simmering water (don't let bowl touch the water). Allow to melt, then stir very gently until smooth. Set melted chocolate aside to cool slightly.

• 3.
  Meanwhile, whip the cream to soft peaks, then fold in the cooled chocolate, then fold in the cooled chocolate.
• 4.
  In a separate bowl, whisk the eggs and 2 tablespoons sugar using electric beaters until pale, then whisk in the mascarpone. Carefully fold a quarter of the chocolate cream into the mascarpone mixture, then fold in remaining chocolate cream. Cover and refrigerate until needed.
• 5.
  Combine coffee, Kahlua and remaining 1 tablespoon sugar in a shallow dish.
• 6.
  One at a time, briefly dip 8 of the sponge fingers into the coffee mixture and lay in a row on a flat serving platter. Using a palette knife, spread half the mascarpone mixture on top, then scatter with half the raspberries. Top with another 8 dipped sponge fingers, remaining mascarpone and berries, followed by the remaining 8 dipped sponge fingers. Cover loosely and chill for at least 2 hours or overnight.
• 7.
  For the chocolate sauce, place chocolate in a bowl. Place cream in a pan over medium heat and bring to just below boiling point. Pour over chocolate, then stir until smooth. Serve warm. (If necessary, reheat in a heatproof bowl set over a pan of simmering water). Store in the fridge for up to 1 week.
• 8.
  When ready to serve, drizzle tiramisu with the chocolate sauce and cut into 8 slices. Alternatively, dust the top with some cocoa powder and serve chocolate sauce in a bowl on the side.