This simple method for tempering chocolate will give you smooth, shiny hot cocoa bombs. Use a good-quality bittersweet chocolate with at least 70% cacao for best results. You can make the bombs ahead of time, but wait until right before serving to cover them in the webbing.
Two 1.38-ounce packages hot cocoa mix (without marshmallows)
18 to 24 pumpkin spice marshmallows, such as Jet-Puffed
6 small candy ghosts
6 small candy spiders
1 to 2 tablespoons chocolate sprinkles
6 regular marshmallows
12 candy eyes or 6 additional candy spiders, for decoration, if desired
Milk, for serving
Direction
Special equipment: an instant-read thermometer; 2 large 6-cavity silicone hot chocolate bomb molds (2 1/2-inch diameter cavities); a small food-safe brush; latex gloves
To temper the chocolate: Put 8 ounces of the chocolate in a double boiler over low heat. Heat, stirring, until the chocolate is almost melted (about 100 degrees F on an instant-read thermometer). Remove from the heat and add the remaining chopped chocolate in 2 or 3 additions, stirring until melted. The tempered chocolate will be thick and about 90 degrees F.
Divide the chocolate among 2 large 6-cavity silicone hot chocolate bomb molds (2 1/2-inch diameter cavities). Use a small brush to brush the chocolate up the sides, making an even coat on the sides and in the bottom. Make sure the sides are thick enough all the way to the edge of the molds. Let sit at room temperature until completely set, 20 to 30 minutes. (If it is very hot, you can pop the molds in the refrigerator for a minute or two to finish.)
Wearing latex gloves, gently remove the chocolate half-spheres from the molds. Set on a piece of parchment paper on your work surface. Divide the hot cocoa among 6 of the half-spheres, then add 3 or 4 pumpkin marshmallows, 1 ghost, 1 spider and 1/2 to 1 teaspoon sprinkles to each of the same half-spheres.
Warm a small nonstick skillet over very low heat. To seal the bombs, set an unfilled half-sphere on the skillet open-side down for just a second to warm the chocolate. Set on top of a filled half-sphere, matching the seams as much as possible. Repeat with the remaining half-spheres. Let sit until hardened, about 5 minutes.
To make the marshmallow webs: Put the regular marshmallows in a small microwave-safe bowl. Microwave until the marshmallows inflate and soften, 10 to 15 seconds. With gloved hands, pull up a little bit of marshmallow and stretch between your fingers to make thin webbing. Stretch the webbing over and around the bombs. Continue to pull and stretch the marshmallow until all of the bombs are covered in webbing. Add 2 candy eyes or a spider to each, if desired.
To serve, heat 6 to 8 ounces milk per bomb until very hot. Add to mugs and drop in the bombs. Enjoy, stirring to melt the chocolate.