Preheat oven to 325°.  Line 2 baking sheets with parchment paper or Silpat. Spread 1/4 cup hazelnuts in a skillet or pie plate and toast for about 3 to 5 minutes or until lightly golden brown.

In a food processor, pulse the remaining 1/2 cup hazelnuts with 2 tablespoons sugar intil finely ground. Add the flour, cinnamon, allspice, cloves, salt, and the remaining 1/2 cup plus 2 tablespoons sugar and pulse to combine well. Add 1 cup butter, broken into hunks, and orange liqueur and pulse until the dough comes together.

On a lightly floured surface, working with half of dough at a time, roll the dough out to about 1/4 inch thick. Using a 1 1/2- to 2-inch cookie cutter, cut cookies out as closely together as possible. Place cookies on baking sheet, about 1/2 inch apart. Repeat with remaining half of dough, gently kneading in scraps from first half. Gather scraps from second half, gently knead, and reroll scraps from second half.

Bake the cookies for about 20 minutes, until the bottoms are lightly colored but the tops are still fairky light, rotating pans after 10 minutes. Transfer the baking sheets to wire racks and allow to cool.

In a medium saucepan over low heat, melt the chocolate with the remaining 6 tablespoons butter, whisking until smooth. Transfer the mixture to a medium bowl and let cool for 10 minutes.

Turn half the cookies over and spoon a small dollop of the chocolate in the center of each of those. Dip the remaining cookies halfway into the chocolate and position over the filled bottoms, pressing gently to seal. Sprinkle the remaining chopped toasted hazelnuts onto the chocolate, pressing gently if necessary, and let the sandwich cookies stand for about 30 minutes until the chocolate is set.  Chill if packaging or transporting.