I rarely use heavy cream because it's way too rich. I would recommend 50/50 aka Half & Half, but use a slurry to thicken it.
Add a good veggie broth or chicken/beef broth. I usually make my own from scratch.
Make sure not to let it boil for more than 10 minutes max after you add the slurry mixture.
Slurry - some sort of powdered starch like corn/potato mixed with cold water. Mix before adding to your soup/etc....
Bring to a boil to thicken/expand the starch molecules.