Or, unless the inner Nigella (although it's not a Nigella recipe) and try this one?:
http://www.ditchthecarbs.com/2014/12/08/frozen-white-christmas/ . At the described portion size, it's only 5.4gr of carb, although it's richness is reflected in the calories if that's a consideration.
If you want to control portion size, you could do it in dariole moulds or smaller ramekins, lining them with cling film before freezing, then removing the mould/ramekin once frozen to get those back, and make storage more efficient?