Preheat your oven to 180ºc/160ºcfan and line a muffin tray with 12 cases
Add the butter and sugar to a bowl and beat together until creamy
Add in the self-raising flour, hot chocolate powder and eggs and beat until smooth
Split between the cases and bake in the oven for 19-21 minutes until cooked through
Leave to cool on the side.
Marshmallow Frosting
Add the egg whites to a large bowl and start to whisk to stiff peaks
Add the 100g of caster sugar, 1 tsp at a time, whilst whisking.
Once all the sugar is in, whisk in the vanilla and leave the meringue to whisk on a slow speed just to keep it moving and stop it from sitting.
Whilst this is whisking, add the other 100g of caster sugar to a pan with the water. Heat this on a low heat to dissolve the sugar.
Once the sugar is dissolved, turn up the heat and boil the mixture to 113ºc.
Once heated, turn the whisk up high again and trickle the syrup into the meringue to make the marshmallow. Once all the syrup is in, whisk for a further 5 minutes.
Decoration
Pipe your marshmallow frosting onto the cupcakes however you fancy (I used a 2d closed star piping tip!)
Decorate with mini marshmallows, a flake, and a dusting of hot chocolate powder
Notes
These cupcakes will last for 3 days, but can freeze for 3+ months
The marshmallow is best used fresh, but can be kept for 2-3 days in the fridge and re-whipped before use.