Cream the butter, brown sugar and vanilla in a stand mixer until light and fluffy (about 2-3 minutes). Scrape the sides of the bowl to make sure all ingredients are blended.
Add in the egg and beat until combined.
Add in flour, baking soda, ginger, nutmeg, cinnamon and salt. Stir until all combined and the dough forms a ball.
Flour your work surface and roll out the dough to 1/4 inch thickness. Cut out cookies using a pumpkin cookie cutter and carefully transfer them to a parchment lined baking sheet or use a silicone baking mat on the sheet. Using a paring knife, cut out eyes and a mouth on HALF of the cookies - these will be the tops. Leave the other half of the cookies whole - these will be the bottoms. Place the cookies in the freezer for 15 minutes and freeze until firm.
Preheat oven to 350 degrees. Bake the frozen cookies for 8-10 minutes and just golden brown. Remove from oven and cool on baking pan for 10 minutes and then transfer to a cooling rack and cool completely.
Add the 1 TBSP of butter to a small saucepan and melt until slightly brown - takes about 2-3 minutes. Remove from heat and let cool for 5 minutes. Brush butter over the top half of the cookies with the eyes and mouths cut out. Sprinkle with cinnamon sugar.
COOKIE ASSEMBLY: Carefully spread the melted dark chocolate over the bottom half of the cookies (the cookies with no eyes or mouth!). Place the top cookies (pumpkin face) over the chocolate and gently press down. This should create about 12 sandwich cookies depending on the size of your cookie cutter.Cookies can be served immediately with the melted chocolate or you can wait until the chocolate firms up to enjoy. Putting them in the refrigerator to cool the chocolate completely is another great way to enjoy these cookies.