I can't eat raw butter (I use it to cook) so buttercream has always made me gag.
But I've discovered the secret- un salted butter and my lovely Kenwood mixer.
I leave it whisking away (silicone blade beater) for 8-10 minutes.
It's the Cat's Pyjamas! 
So... I've dome the swirl of buttercream on a cupcake thing.
No-one really eats large cakes in my house.
What about Vienesse Whirls? How do I make them (with jam and creamy icing in them)
TIA .