This is *the* best hot chocolate I've ever tasted.
Any brand of syrup (most are vegan) will work, though I'm not sure if the pump amounts are the same. Praline is my favourite - I'm not a fan of 'toasted marshmallow' syrup or ones designed more for coffee (butterscotch, gingerbread etc). I've blogged previously about using Kahlua or Creme de Menthe instead which is also good, but alcoholic too.
Whilst you can make hot chocolate simply by heating milk; microfoaming it with an espresso machine's steam wand will give you a much better mouth feel. Always add the syrup to the milk before steaming - that way the foam contains the flavour and doesn't go all beany.
This recipe doesn't strictly need marshmallows, but they're a good addition if available. I've found its better to melt them in advance - otherwise you don't really pick up their taste and end up having to eat them separately at the end with a spoon. I use a blow torch because it's quickest and more fun than using a lighter. The best brand I've tried are Alternative Stores (sold online and in Vx). The only brand I wouldn't recommend is Anandas - all that we've tried (from One Earth shop in Birmingham) have tasted stale.
Kinnerton Dark is in most supermarkets, is cheap and has a fairly low cocoa content, making it less bitter than say 70%. You can use the chocolate of your choice, but the trick I learnt through trial and error it to not add too much. Otherwise it won't dissolve properly and you loose some of the hazelnut flavour.
If you've a food processor then I highly recommend using it to grate an entire bar of chocolate, then store it in a small tupperware and use it for icecream and topping hot chocolate. We recently acquired a bag of Montezumas hot chocolate shavings which give the same effect, though costs quite a bit more.
Method: Pump the syrup into a large mug, break up the chocolate and add, then cover with soya milk. Microfoam to about 70 degrees:
Stick a spoon in and give it a good stir under the surface so that the chocolate incorporates into the milk without destroying the foam:
Toast the marshmallows, then float on the surface:
Top with squirty cream and shavings:
Enjoy immediately! :-)