The short answer to your question is ice-cream is both countable and non-countable.
The substance (which contains cream, sugar, egg) of the ice-cream of course is non-countable. And in fact if you check dictionaries, many of them say there is no plural form for ice-cream.But the entire package of “ice-cream on a cone” or “ice-cream in a cup” are countable.
If you go to an ice-cream parlor and order "Two ice-creams, please", the server would not scream at you, "What did you say? 'Ice-creams' is bad English. I don't serve a stupid person that uses bad grammar."
In my search over the internet, there are 92.3 million hits on “ice-creams”. So “ice-creams” is perfectly acceptable English.
