Grease a 9×9″ square non-metal baking dish (I like to use baking spray, but a small amount of neutral oil will work great). Set aside.

Add the gelatin and 2/3c cold water to the bowl of a stand mixer fitted with the whisk attachment. Let stand at least 5 minutes.

4 packets unflavored gelatin,2/3 c cold water

In a small bowl, whisk together the cocoa powder, boiling water, espresso powder, and vanilla extract until well combined and glossy.

1/4 c Dutch cocoa powder,1/2 tsp espresso powder,2 tsp vanilla extract,1/4 c boiling water

 

In a 1 1/2-2 qt saucepan, stir together granulated sugar, corn syrup, salt, and 2/3 c water. Heat over medium heat, stirring until sugar dissolves. Then raise to medium-high heat and continue cooking, without stirring, until it reaches 250°F on a candy thermometer.

2 c + 2T granulated sugar,2/3 c light corn syrup,1/2 tsp kosher salt,2/3 c water

Meanwhile, add the cocoa mixture to the gelatin mixture, mixing at low speed until combined.

Once the sugar syrup comes up to temperature, slowly pour it into the chocolate-gelatin mixture, beating at low speed until all the syrup is added. Raise the mixer speed to high and beat until thick and fluffy (about 10-15 minutes). You’ll know it’s ready when it starts to pull away from the sides of the bowl.

Pour into your prepared pan, using a spatula to scrape the bowl well and smooth out the top of the marshmallows.

In a small bowl, sift together the 1/3 c cocoa powder and 1/3 c powdered sugar, then stir it until it’s fully combined. Then use your sifter to dust the top of the marshmallows. Cover lightly with aluminum foil and let sit at room temperature overnight (or about 8 hours).

1/3 c Dutch cocoa powder,1/3 c powdered sugar

The next morning, turn the marshmallows out of the pan onto a cutting board. If the edges of your pan are rounded, and you want straight sides on your marshmallows, cut the edges off of the marshmallow slab first (a snack for the chef!).

Then cut evenly into 16 marshmallows (or more if you want smaller ‘mallows). Tip: lightly grease the knife with some neutral oil beforehand and in between cuts to keep it from sticking too much.

Toss marshmallows in the cocoa powder-powdered sugar mixture.

Store marshmallows in an airtight container at room temperature. Stored like this, the marshmallows can last for at least 3 weeks (although I’ve actually eaten them 6 weeks later and they’re still great!).