Storage advice for icing containing diary

[ReallyNotsobad]

Hi,

I am baking a cake for a bake sale. The icing will contain the following Ingredients Unsalted butter, powdered sugar- Dutch processed cocoa powder - Salt - tiny pinch
Heavy/double cream -180 ml
Vanilla extract

The iced cake will be refrigerated all night, than taken to the venue in the morning. Is this safe to be left at room temperature sliced in sealed tubs for up to a day? It could potentially be out 6-8 hours.

Sorry I should have mentioned that there will be 150g of icing sugar to the 180ml of heavy cream.

That's a hell of a lot of liquid for 150g of icing sugar, are you sure that's right?

It is proper fudge icing made in a sauce pan, it firms in the fridge. It is beautiful, and melts in your mouth.

So it's been cooked too?
I'm sure it will be fine left at room temperature for a few hours.

My butter is always left out on the worktop rather than the fridge so it would just be the cream I would consider but if it's been cooked and combined with the other ingredients then I wouldn't worry about it

I was wondering why you had icing in your diary… ?

Sorry, confused?

You put Diary in your title

Oh haha, so I did, had no sleep last night, and it shows! I've ended up using a bog standard buttercream instead to be on the safe side. It is for macmillan cancer support, and I don't want to make people sick!