Too much port in sauce I overshot the port and the taste is overpowering. There is also cream and heavy cream in there, as well as black truffles. 

Is there any way to fix it?
You can always create a larger batch. If you, for example, doubled the amount of port, you can add* all the other ingredients in the same amount you originally used and that would correct the proportions.

*Depending on the recipe and how things are put together, you may need to do more than simply add. You might need to create an new starter and then mix them together.