What icing do I need please? What is this called?

[W00t]

I want to make the type of 'icing' that goes inside a chocolate Swiss roll. All the recipes I've seen use whipped cream, but half of us can't eat dairy, and the other half hate cream!
I really like the fake white stuff inside shop-bought Swiss roll, but no idea what it is. Is it meringue icing? Or is that something else entirely?
Thanks to all the knowledgeable bakers out there.

(And did MNHQ get rid of the "baking" topic, I could only find food/recipes )

@YetAnotherSpartacus

Didn't it use to be called 'mock cream'?

Confectioners cream, I think.

I once had a very bizarre conversation with the guy on the cake counter somewhere because DH wanted a cream slice but only if it had fake confectioners cream in it, and I was asking if it was confectioners cream and he kept saying "no, is nice cream" "but is it fake cream" "iz nice cream" because he'd never heard of the term.

The recipe I was thinking of was mock cream. I looked it up. It was from the 50s.