A half-sphere mould. That’s the only bit of kit you can’t improvise. The rest is chocolate, hot chocolate powder, a handful of mini marshmallows and a warm plate.
I’d go for silicone rather than the hard plastic kind. With silicone you can push each dome out from underneath, which matters when the shell is a couple of millimetres of chocolate. With a rigid mould you’re relying on the chocolate shrinking away from the sides, and that only happens properly if it’s tempered.
Making them, start to finish
Paint, don’t pour. Melt your chocolate, then brush or spoon a layer up the inside of each cavity. Chill it for ten minutes, then do a second coat, paying attention to the rim. The rim is where thin shells break when you lift them out.
Push from the bottom. Once the shells are firm, peel the mould back and press up under each dome. Handle them as little as you can, because warm fingers leave prints.
Fill half of them. A spoonful or so of hot chocolate powder and a few mini marshmallows go in six of the halves. Don’t overfill, or the two halves won’t meet.
Seal on a warm plate. Warm a plate in the microwave or with hot water, dry it, then touch an empty half to it rim-down for a second. The edge melts slightly, and you press it onto a filled half straight away. Run a finger round the seam and you’re done.
To serve, drop one in a mug and pour hot milk over it. If you make your milk in a pan, a proper milk pan that doesn’t catch on the bottom makes the whole thing less of a faff.
The mould itself
The reakoo half sphere silicone mould comes as two moulds with six cavities each. That’s 12 halves, or six finished bombs per round. Each cavity is 5cm across and each mould measures about 19 x 13cm, so they both fit on a dinner plate in the fridge. It’s food-grade silicone that the listing says is fine in the oven, fridge and dishwasher.
That 5cm is smaller than the big bombs you see in coffee shops. I don’t think that’s a problem. A 5cm bomb sits comfortably in any mug, a mugful of hot milk melts it properly, and it’s a sensible size for children. If you want a showpiece that half-fills a giant mug, look for a 6.5cm or 7cm mould instead.
Worth the bother?
For a December weekend with kids, I’d say yes. It’s an afternoon job with a fun ending, and the moulds are just as happy doing mousse domes or jelly later. As a gift, a box of six homemade bombs looks like far more effort than it was.
The one honest downside: chocolate that isn’t tempered can bloom (go dull and streaky) and soften in a warm room. If you want them glossy for a few weeks, it’s worth learning to temper. If they’re getting eaten this week, plain melted chocolate kept somewhere cool is fine.
