Does anybody know if it is ok to mix buttercream and double (heavy) cream together?

I am topping a cake but buttercream alone can be too sweet. Do you think the two together will work and how would I do it. Would I beat the double cream first till it was thick then add it or mix it into the buttercream while it is still liquid to get the correct consistency?

Thanks

I don't know about the buttercream recipe you use but the one I make uses heavy cream. I would say it's OK but becareful of the amount you use. It could go flat quick.

Would you mind sharing your recipe?