Combine hot water, the ½ cup cocoa powder for the marshmallows, and espresso powder. Stir until dissolved. Set aside.
1 cup hot water, ½ cup cocoa powder, 1 tablespoon espresso powder
Line an 8x8 baking pan with parchment paper. Combine the powdered sugar, cornstarch, and cocoa powder in a small bowl. Dust about half the mixture over the bottom of the pan, and on the sides if possible. Set the rest aside.
½ cup powdered sugar, ¼ cup cornstarch, ¼ cup cocoa powder
In the bowl of a stand mixer with the whisk attached add the gelatin and lukewarm water, and set aside. (Do not stir.)
1 cup lukewarm water, 2 ½ tablespoons unflavored gelatin
In a medium to large saucepan, combine the chocolate espresso mixture, sugar, and corn syrup and stir.
1 ½ cup sugar, ½ cup corn syrup
Cover and heat the mixture over medium heat for 5 minutes, then remove the lid and attach a candy thermometer. Continue heating until the mixture reaches 240℉, stirring frequently. Remove from heat.
Start the mixer on the lowest possible speed and slowly stream in the hot mixture.
Once all of the hot mixture is added, slowly increase your mixer speed (carefully to avoid splatter!) Once the mixer is up to full speed, beat for 10-12 minutes.
Pour the marshmallow mixture into the prepared pan, dust the top with the remainder of the powdered sugar mixture and let set for at least 4 hours or overnight.
Cut into cubes or shapes as desired, and enjoy!
Notes
Be sure to stir the hot mixture frequently to prevent it from bubbling over. It can take some time for the mixture to reach 240°F, but it will get there! It's important that you be patient as removing it from the heat too early (or too late) can impact the texture of your Chocolate Marshmallows.Try using cookie cutters to cut the marshmallows into fun shapes!