Polycarbonate are the most rigid and durable of molds you can use with chocolate. They come in various shapes to make all kinds of chocolates, from large bars to miniature shapes. These are slightly smaller than bombs you make using silicone or 3 part molds but still fit into a standard sized mug really nicely and are big enough to fit lots of fillings.
For traditional hot chocolate bombs, we'll need the domed shaped molds, which come in a few sizes. The ones I'm using is in this tutorial makes spheres that are 2.5 in (63mm) diameter (the manufacturer that makes these molds here refer to this mold as "large" sized). I got mine from Amazon here.
These type molds are used by professional bakers and chocolatiers and are the most expensive of the three types. They are, however, going to be the most durable for long lasting use. Also the rigidity of the mold has its perks - you'll be able to scrape these things clean of chocolate without harming the chocolate inside each cavity.
If you're looking for tools you need to make the bombs, as well as chocolate types to use, or shipping questions, check out my "Hot chocolate bombs: your complete guide" post, which covers covers more of the basic questions around hot chocolate bombs.
Compound chocolate has this really interesting characteristic that when it gets really hot it thickens up. It sounds counter-intuitive, because I want to think that as we "melt" ingredients, they should get more runny. It's a pretty simple fix - you didn't burn your chocolate (until you see that it has black spots, in which you will have to throw it out.) You just have to let it cool down. The ideal working temperature for most compound chocolates is around 100F (32C). You don't need a thermometer at all to work with compound chocolate - but just wait until it cools by gently stirring it in your bowl. It will go back to it's fluid state, I promise.
If you really want to heat up your chocolate, you can caramelize your white chocolate, which is insanely yummy. Even though compound chocolate is not real chocolate, it still works! (Some people believe that caramelized white chocolate is dependent on the cocoa butter content, but it's really dependent on the presence of sugar ;) )
This is probably the number issue with these molds. As chocolate cools, it naturally contracts or shrinks as it hardens. This happens with real chocolate, and probably with compound chocolate as well. (Compound chocolate has different fats, so I'm not totally sure, but it acts similar to real chocolate)
If you have trouble removing the chocolate easily, it is because the chocolate has not set completely. The first time I used these molds I could not, for the life of me, get them out. Turns out I wasn't being patient enough in letting them set completely.
If all else fails put your molds with the compound chocolate in them in the freezer. It was almost comical how easy they were to take out when set completely.
Warm hands, warm heart! But yeah, problematic when working with chocolate. Some people swear by keeping ice nearby to chill their hands when working with chocolate, some people wear gloves. Both those methods can help. You can also try to touch the chocolate as little as possible. Compound chocolate has a higher melting temp than real chocolate (which coincidentally melts at body temp - a key feature as to why it melts in your mouth so wonderfully when you eat it) so at least we have that to our advantage. So when you pop them out of the mold, do it onto the counter top and then use the silicone muffin cups to handle your chocolates.
For every chocolate bomb (an entire bomb with marshmallows and cocoa powder) you will need
So for instance, if you wanted to make 3 hot chocolate bombs, you'll need 120g of chocolate, 27g of hot cocoa mix, and 27g of marshmallows.