I wanted to use a good filling for my son's birthday cake but I will not be able to refrigerate it since its going to be a big one.

I was planning to assemble the cake the night before the birthday party and leave it out on the counter.

Which fillings would you guys recommend that can be left at room temperature? I don't really want to use jams. I know ganache is an option and I was thinking whipped ganache.

Are there any other options? Fruit? Any good flavored buttercream?

Thanks for your help!

I usually follow the Rule of refigeration. If it needs to refigerated outside of the cake, then it needs to refigerated when it's in the cake. Milk based or egg based fillings should be refigerated. I put fresh strawberries inbetween cakes all the time and I don't refigerate them. I also use bettercreme that I make a whipped topping from and I don't refigerate it.

I mix sleeved fillings with my whipped bc. Works great.