In two small, microwave safe bowls, melt semi sweet and white chocolate chips in 30 second increments stirring in between. It should take about 60-90 seconds. Alternatively, you can use a double boiler.
Spoon about 1 tablespoon of each into each half sphere mold. Using the back of a spoon or a pastry brush, gently swirl the chocolate together for a marbled effect and spread to coat the sides. Don’t swirl more than 4 times in each mold as the colors will mix and be indistinguishable.
Let set in the fridge or the freezer for 10-12 minutes or until hardened.
Reinforce the edges with a little of the remaining chocolate. Let set until hardened.
Carefully remove each half sphere from the molds. Be sure to handle each half sphere very little as the chocolate will melt from the warmth of your hands and fingerprints will be visible.
In 6 of the half spheres, spoon 1 tablespoon of the hot cocoa powder.
Top with 1 teaspoon of the espresso powder and a couple mini marshmallows.
Warm a small plate in the microwave for 45 seconds. Place an empty half sphere on the plate for a few seconds until the edge begins to melt.
Place empty half onto the corresponding filled half sphere ensuring that the edges are aligned. Run a clean finger around the edge to clean up any excess melted chocolate. Let set for a minute. Repeat with remaining 5 spheres until all of the cocoa bombs are assembled.
To make hot cocoa, place a cocoa bomb into a mug and top with 6 oz of warm milk or water.
Once the shell has melted, stir to emulsify. Serve immediately and enjoy!
Swirling these two flavors together imitates a black and white mocha coffee you could get from a coffee house. Be sure to use Ghirardelli’s white chocolate chips as they are the best and easiest to melt. Generic white chocolate will seize easily when being melted causing frustration and waste.