In the bowl of a stand mixer fitted with a beater attachment, or in a large mixing bowl using a hand mixer, beat the butter and sugar on medium-high until well combined and fluffy, about two minutes.

Add the corn syrup, vanilla extract and peppermint extract. Mix until combined, then beat in the espresso powder, salt, baking soda, salt and cocoa powder.

Mix in the flour until the last streaks of white disappear.

Dump the dough onto a sheet of parchment paper about the size of a half sheet tray, then cover it with another similar-size piece of parchment. Using a rolling pin, roll out the dough in between the sheets to a about a 1/4-inch thickness.

Set on a flat surface like a half sheet tray or large cutting board and transfer to the refrigerator or freezer to chill until very firm, about 15-30 minutes. Preheat the oven to 350°F.

Once the dough as chilled, use a small circle cookie cutter (I used a 1.75-inch) to cut out as many rounds as you can from the dough and transfer to a half sheet tray lined with parchment paper. Chill the cutouts in the freezer or fridge until they are very firm. Bundle up the scraps and cover in parchment to roll out again. Cover and chill again.

Bake the cookies on the middle rack for 11 minutes and immediately transfer to a cooling rack. Repeat with the remaining dough.

While the cookies cool, make the marshmallow filling. Pour 3 tablespoons of water into the bowl of a stand mixer fitted with a whisk attachment. Cover the surface of water very evenly with the granulated gelatin, ensuring it all gets moistened. Add just a few drops of extra water to wet any dry gelatin.

To a small saucepan, add the corn syrup, then the sugar and vanilla bean seeds. Drizzle in the water, trying to evenly moisten the sugar. Use the probe of an instant-read digital thermometer or the back of a wooden spoon to stir together the ingredients, then transfer to the stove to cook over medium-high heat.

Cook the syrup without stirring until a candy thermometer or instant-read digital thermometer reads between 240-245°F. Immediately remove from the heat, turn the mixer to low speed and begin slowly drizzling in all the molten sugar down the side of the bowl. Once all the syrup has been added, turn the mixer to high speed and allow to whip for 12 minutes. Once the mixture is whipped up and the bowl of the mixer is just barely warm to the touch. Add in the vanilla bean paste (if using) and peppermint extracts and whip for a few seconds just to combine. Transfer to a piping bag with a small round tip (or even a zipper bag with a corner snipped off).

Flip over half of the cookies and pipe about a tablespoon of filling onto each of them, leaving a slight border. Use the remaining cookies to sandwich the filling, pressing down just enough to push the filling to the edges. (If the filling is too loose or stringy, just wait 5 minutes so it can continue to cool and set and try again.)

Add the chocolate to a glass, plastic or silicone mixing bowl and heat in the microwave in 5 second bursts, stirring in between each burst, just until about 90 percent of the chocolate has melted. Allow it to finish melting as you stir. (Or you could also melt the chocolate in a heat-safe bowl over a saucepan with an inch of simmering water.) Transfer the chocolate to a small glass or bowl. Dip each cookie sandwich one-third in, return to its parchment-lined sheet baking sheet, and sprinkle with crushed candy canes or peppermints. Allow the chocolate to set and the marshmallows to cure for about an hour in a cool, dry place.