Melt chocolate in top of double boiler over hot, not boiling, water.
Remove from heat; cool.
Cream butter, melted chocolate, granulated sugar, egg and vanilla in large bowl until light.
Combine flour, cinnamon, baking soda and salt in small bowl.
Stir into creamed mixture with sour cream until smooth.
Cover; refrigerate at least 30 minutes.
Preheat oven to 400°F.
Lightly grease cookie sheets or line with parchment paper.
Roll out dough, one fourth at a time, 1/4 inch thick on lightly floured surface.
Cut out with cookie cutters.
Place 2 inches apart on prepared cookie sheets.
Bake 10 minutes or until lightly browned, but not dark.
Remove to wire racks to cool.
Prepare Decorator Icing.
Spoon into pastry bag fitted with small tip or small heavy-duty plastic bag.
Decorate cookies with icing.