Temper the White Chocolate:

1. Finely chop the white chocolate.
2. Melt it gently using a double boiler or in the microwave in 15-20 second intervals, stirring regularly to prevent burning. The temperature should reach 40-45°C (104-113°F).
3. Let the chocolate cool to 26-27°C (79-81°F), stirring frequently.
4. Then, slightly reheat the chocolate to 28-30°C (82-86°F) to temper it.

Form the Shells:

1. Using a pastry brush or the back of a spoon, apply a layer of chocolate into the cavities of a silicone mold. Ensure the layer is even and covers the edges.
2. Let it harden at room temperature or in the fridge for 10-15 minutes.
3. Apply a second layer to strengthen the shells, then let it harden again.

Unmold the Shells:

1. Once fully hardened, gently unmold the chocolate shells.
2. Place them on a clean surface and separate them into two groups: one half for the base and the other for the top to close the bombs.

Fill the Shells:

1. Fill each bottom shell with 1-2 tablespoons of sweetened cocoa powder, mini marshmallows, and any other fillings you like (candies, spices, etc.).

Seal the Bombs:

1. Heat a plate in the microwave for 1 minute.
2. Place the edge of the top shell on the warm plate for a few seconds to slightly melt the chocolate.
3. Immediately assemble with a filled shell, gently pressing to seal.
4. If needed, smooth the seam with your finger.

Decorate the Bombs:

1. Using a piping bag or spoon, decorate the top of the bombs with melted chocolate.
2. Sprinkle immediately with sugar pearls, candy bits, or festive decorations.