Melt the chocolate according to package directions.
Start with a clean and dry silicone mold on a tray.
Pour the chocolate into each well and use a spoon to evenly spread the chocolate right up to the edges.
Place the tray in the freezer for 5-10 minutes.
Remove from the freezer and add a second layer of chocolate anywhere that seems a bit thin, especially around the top rim of the circle.
Return to the freezer for 5 more minutes.
Remove the chocolate halves from the mold and set them on to the chilled tray from the freezer. Then gently melt the edges of the circles on a hot plate so you’ll have a smoother seam between the two halves. Repeat with the other halves.
Add the marshmallows and caramel to half of the cups.
Heat the edges of the empty halves again, one at a time, and set them onto one of the filled halves.
When all of the bombs are filled and sealed together you can drizzle the remaining melted chocolate on top.
Immediately sprinkle with the flake salt.
Set the finished bombs back in the fridge or freezer for a few minutes to help the chocolate drizzle harden.
To use the bombs: Heat milk to around 140 degrees Fahrenheit and carefully pour over the top of the bomb and then stir until smooth. Or store at room temperature in an airtight container for up to a week (because of the caramel).