
Combine butter and sugar in a large mixing bowl (or the bowl of a stand mixer fitted with paddle attachment) and use an electric mixer to beat together until creamy and well-combined.
Add molasses, vanilla extract, ginger, cinnamon, cloves, and cayenne pepper and stir together until all ingredients are thoroughly incorporated.
Add egg and stir well.
In a separate, medium-sized bowl, whisk together flour, baking powder, baking soda, and table salt.
Gradually add the dry ingredients into the wet ingredients (I do this in 3 or 4 parts), stirring until just combined after each addition.
Cover dough tightly with plastic wrap and transfer to the refrigerator to chill for at least 30 minutes and up to 2 days.
When cookie dough is almost done chilling, preheat your oven to 350F (175C) and line baking sheets with parchment paper.
Once dough is chilled and oven is preheated, scoop dough by 1 ½ Tablespoon-sized scoop (27g) and roll gently between your palms to create a smooth surface (if dough is too sticky to roll, return it to the refrigerator to chill a bit longer). Roll cookie dough through granulated sugar and place on prepared baking sheets, spacing at least 2” (5cm) apart.
Transfer to center rack of preheated 350F (175C) oven and bake for 10 minutes. Cookies may appear slightly underdone in the centers when finished. It's best if the edges are not browning or at most are just turning a very very light golden when finished, as over-baking will make the cookies dry and crisp when they should be soft and chewy.
Allow cookies to cool completely on baking sheet (they will be fragile when warm) before filling.
Add chocolate to a small, microwave-safe bowl and heat in microwave for 30 seconds. Stir, then return to microwave in 15-second instruments, stirring in between, until chocolate is completely melted and smooth. Set aside and allow to cool (stirring occasionally) until chocolate is still melted but no longer warm to the touch before proceeding.
Place butter in a medium-sized mixing bowl and use an electric mixer to beat the butter until creamy.
Add melted, cooled chocolate and stir on low-speed until well combined.
With mixer on low-speed, gradually stir in powdered sugar. Be sure to scrape the sides and bottom of the bowl periodically to incorporate all ingredients.
Add vanilla extract and salt and stir again.
Once cookies are completely cooled, scoop 1 Tablespoon of filling (14g) onto the bottom of one cookie. Top with another cookie to make a sandwich and press the cookies together gently but firmly to distribute the frosting in the cookie. Repeat with the remaining cookies. Enjoy!