Hot Chocolate Bombs

Before you start

A hot chocolate bomb is a hollow chocolate shell holding cocoa mix and marshmallows. Pour hot milk over it and the shell softens, splits and releases the filling. The whole trick lies in the shell: thick enough to lift from the mold without cracking, thin enough to give way in a mug of hot milk, and tempered so it stays glossy and snaps at room temperature.

Tempering means melting chocolate and then cooling it under control so the cocoa butter sets in its stable form. This recipe uses the seeding method, which needs only a thermometer and some patience. If tempering feels like too much, compound coating chocolate sets without it, at the cost of a waxier flavor. Silicone sphere molds about 6 cm (2½ inches) across are the right size for a standard mug.

Ingredients

• Shells300 g (about 2 cups chopped) dark or milk chocolate — good-quality bar or callets, not chips
• Filling6 tbsp (about 80 g) hot cocoa mix — homemade or store-bought
• 1 cup (about 50 g) mini marshmallows
• 2 tbsp sprinkles or crushed peppermint — optional
• Decoration30 g (1 oz) white or contrasting chocolate — optional, for drizzling
• To serve240 ml (1 cup) per bomb whole milk — heated, for serving

Method

1. Chop the chocolate finely and set aside about one third as seed chocolate. Melt the remaining two thirds over barely simmering water or in short microwave bursts until it reaches 45°C to 50°C (113°F to 122°F) for dark, or about 45°C (113°F) for milk chocolate.
2. Off the heat, stir in the seed chocolate a little at a time until the mixture cools to 31°C to 32°C (88°F to 90°F) for dark or 29°C to 30°C (84°F to 86°F) for milk. Remove any unmelted pieces. Test by smearing a little on foil: it should set glossy within about 5 minutes at cool room temperature.
3. Spoon about 1 tablespoon of chocolate into each cavity and spread it up the sides with the back of the spoon or a brush, reaching right to the rim. Turn the mold upside down over parchment for a moment so excess drips out, then scrape the top edge clean.
4. Chill the mold for 5 minutes, then add a second, thinner coat, paying attention to the rim where shells usually crack. Chill again for 5 to 10 minutes until fully set and the chocolate pulls away slightly from the silicone.
5. Wearing gloves so fingerprints do not melt the surface, peel the mold back from each half and press the shell out gently from the bottom. Keep the halves on a cool tray.
6. Fill six of the halves with 1 tablespoon cocoa mix, a small handful of marshmallows and a few sprinkles. Do not overfill, or the lid will not sit flat.
7. Warm a plate until it feels hot to the touch. Touch the rim of an empty half to the plate for 2 to 3 seconds to melt the edge, then set it on a filled half and run a gloved finger around the seam. Drizzle with contrasting chocolate if you like and let set for 10 minutes.
8. To serve, place a bomb in a large mug and slowly pour 240 ml (1 cup) of milk heated to about 75°C (167°F) over the top. Wait for the shell to open, then stir until the chocolate is melted.

Tips for success

• A shell about 2 to 3 mm thick is the goal. Two thin coats are stronger than one heavy coat and still melt quickly in hot milk.
• Work in a cool room. A kitchen above about 24°C (75°F) makes tempered chocolate slow to set and prone to streaks.
• Leftover tempered chocolate can be spread on parchment and reused next time; it simply needs to be melted and tempered again.

Substitutions

Tempered chocolate

Compound coating chocolate or candy melts set firm without tempering and are easier for children to work with. They taste sweeter and less chocolatey, so pair them with a strong cocoa filling.

Mini marshmallows

Freeze-dried marshmallow bits stay crisp and do not stick to the shell. A spoon of malted milk powder or caramel bits makes a different surprise.

Whole milk

Oat or other plant milk works if heated to the same temperature. Very thin milks give a less creamy drink once the shell has dissolved.

Variations

Salted caramel bombs

Add a teaspoon of caramel bits or a spoon of thick caramel sauce to the filling and sprinkle flaky salt on the drizzle.

Mocha bombs

Stir ½ tsp instant espresso powder into the cocoa mix for each bomb.

Troubleshooting

The shells crack when unmolded

They are too thin, usually at the rim. Add a second coat, brushing extra chocolate around the top edge, and make sure the chocolate is fully set before peeling.

The chocolate is dull, streaky or soft at room temperature

It fell out of temper, often because it got too warm. Remelt it to the full melting temperature and repeat the seeding step, checking with a foil test before filling the mold.

The bomb does not open in the mug

The milk was too cool or the shell is too thick. Use milk around 75°C (167°F) and pour it directly over the top of the sphere.

Storage

Keep sealed bombs in an airtight container in a cool, dry place around 16°C to 20°C (60°F to 68°F), away from sunlight, and use within about 2 weeks. Avoid the refrigerator; humidity causes sugar bloom and condensation on the surface.

Safety notes

These contain milk and usually soy, and sprinkles or marshmallows may contain other allergens such as gelatin or nuts; label gifts with every ingredient. Check that the milk has cooled to a comfortable drinking temperature before serving it to children.