Melt white chocolate according to package directions. For dipping mint squares, fill custard cups two-thirds full with white chocolate. Melt semisweet chocolate according to package directions. Spoon into second custard cup. Place sheet of waxed paper on baking sheet.
Dip 2 mint squares, at angle, into cooled, but still liquid white chocolate. Hold 2 squares together at right angle, meeting at 2 edges; place on waxed paper so they stand up; seal edge, forming half a box. Repeat with 2 more squares. Once halves of boxes have set up, with tip of a knife, spread a little semisweet chocolate along 4 remaining vertical edges. Gently press together to form box. Spoon about 1 tablespoon melted semisweet chocolate into bottom of box, spreading evenly. Repeat with remaining squares and melted chocolates. Let boxes stand until firm. Store the boxes in the refrigerator.
Puree raspberries with syrup in blender. Force through strainer set over bowl to remove seeds. Reserve 1/4 cup puree for garnish.
Sprinkle gelatin over water in small cup to soften, 5 minutes. Heat in microwave oven or double boiler, stirring, to dissolve gelatin. Stir into raspberry mixture. Let stand until consistency of raw egg whites.
Beat cream and confectioners sugar in bowl until stiff peaks form. Fold into raspberry mixture. (If too loose, refrigerate until thickened enough to pipe; make sure mixture doesnt become too stiff.) Spoon into pastry bag fitted with large star tip.
Pipe mousse into boxes. Pipe any remaining mixture into rosettes on waxed paper; refrigerate.
Scrape any leftover melted white chocolate (remelting if necessary) into small pastry bag fitted with small writing tip. Pipe hearts onto waxed paper. Refrigerate to harden. To decorate, remove from paper with spatula.
Place box in center of each plate. Garnish, if using, with mousse rosettes, hearts, currants. Drizzle with puree. Makes 5 servings.