MAKE THE SUGAR AND STARCH MIXTURE
In a medium bowl, combine the brown sugar, cocoa powder, cornstarch and instant coffee granules (if using) and whisk to combine, then use your fingertips to break up any lumps of brown sugar and whisk again until you have an even mixture. Set the bowl aside.
HEAT THE MILK
In a heavy-bottomed medium saucepan, combine the milk and salt and heat over medium heat until the mixture is steaming and just starting to ripple beneath the surface, about 5 minutes. Remove the saucepan from the heat.
BLANCH AND TEMPER THE EGGS
Add the egg yolks and whole egg to the bowl with the sugar mixture and whisk until combined, then whisk more vigorously until the mixture is several shades paler and voluminous and it falls off the whisk in a slowly dissolving ribbon, about 2 minutes. Whisking the egg mixture constantly, slowly pour about two-thirds of the hot milk mixture into the bowl to temper the eggs, then whisk the warmed contents of the bowl into the saucepan with the remaining milk mixture.
COOK THE PUDDING
In a large heatproof bowl, combine the chopped chocolate and butter and set aside. Return the saucepan to medium heat and cook, whisking constantly and scraping around the sides and bottom of the saucepan, until the pudding is thickened, the foam on the surface has subsided, and it holds the marks of the whisk, about 4 minutes. Stop whisking for a few seconds and check for slow bubbling beneath the surface, indicating the mixture is at a boil, then continue to whisk vigorously for another 15 seconds. Immediately remove the saucepan from the heat and pour the putting into the bowl with the chocolate and butter.
FINISH THE PUDDING AND CHILL
Let the pudding sit for a minute or two to melt the chocolate and butter, then whisk until the chocolate is incorporated and you have a smooth, glossy pudding. Whisk in the vanilla. Press and piece of plastic wrap directly onto the surface of the pudding and refrigerate until it's cold and set, at least 4 hours.
CRUSH THE COOKIES
Place the cookies in a resealable bag and seal, pressing out the air. Use a rolling pin, mallet, or heavy-bottomed saucepan to crush the wafers, breaking them into coarse crumbs with some larger pieces. Set the bag aside.
WHIP THE CREAM
In a bowl, with a hand mixer, whip the cream on low speed to start and gradually increase the speed to medium-high as it thickens, until you have a light, softly textured whipped cream that holds a droopy peak.
ASSEMBLE THE COUPES
Stir the cold pudding to loosen the consistency, then spoon half the pudding into the bottoms of the six coupe glasses. Spoon half the whipped cream on top, followed by the cookie crumbs. Repeat, cover and refrigerate for at least 30 minutes to allow cookies to soften slightly before serving.