Finely chop the white and dark chocolate separately. In a medium bowl, microwave half of the white chocolate at 50 percent power in 30-second intervals, stirring between intervals, until melted, about 2 minutes. Add the remaining white chocolate and stir until completely melted. Repeat with the dark chocolate in a separate bowl. Stir the allspice into the white chocolate. Using a silicone or offset spatula, spread the white chocolate evenly (about 1/4 inch thick) onto a parchment paper-lined baking sheet. Drop dollops of the dark chocolate on top of the white. Using the tip of a knife or skewer, swirl the dark into the white. Sprinkle with the orange peel and raisins. Chill until set, about 30 minutes. Cut into irregular pieces.
The Do's and Don'ts of Cooking with Chocolate