I googled for a smiliar recipe ages ago, found this online and shamelessly lifetd it - don't know what the site was now. Haven't tried it, though.
But I would use cocoa not hot choc - I am sure this (with cocoa) is the recipe my mum used to use, and they were delish...
Chocolate Cornflake Cakes
1oz Margarine
2oz Golden Syrup
1oz Drinking Chocolate (note: NOT Cocoa Powder)
7 Tbsp Cornflakes ("or other crisp ready-cooked breakfast cereal")
Melt fat and syrup slowly in a saucepan. Add the drinking chocolate and heat thoroughly (do not boil). Remove from heat and using a metal spoon, fold in cereal until coated. Spoon into 9 or 10 cake cases and leave to set. It's that easy.
However, for the anxious amongst you, be ready for the stress of stiring in the flakes - obviously, you don't want to stir so vigorously that they all get crushed, yet in order to get enough flakes combined into the mixture, crushing some of them is unavoidable, sadly.
The seven tablespoons rule is rather ambiguous - the range of possible capacities for a tablespoon with this diffuse material is quite broad. I just use great handfuls and judge it by eye, bearing in mind the following:
If you have too many flakes, they won't all be coated, so err on the side of too few. If you have too few flakes, then when they're set, each one will be sitting in a little yummy pool of mixture at the bottom of the cake case. This can be considered rather nice, though if a high yield is your aim, rather wasteful.