Turn your pressure cooker to the SEAR/SAUTE setting. Add butter. Once the butter is melted, add the flour and stir for about 3 minutes.
Add your chopped onion and garlic and cook for another 3-4 minutes or until they become soft.
Add the broth/stock, chopped vegetables, salt, pepper, and cayenne.
Stir until mixed well. Close and lock lid, cook on HI pressure for 3 minutes.
When the timer goes off, unplug the pot and let it naturally release pressure for 5 minutes, and then perform a manual release of the pressure. If soup begins to leak out of the vent, carefully close it and wait a few more minutes.
Plug the pressure cooker back in and turn on to SEAR/SAUTE. Add the heavy cream and stir. Cook for 5+ minutes or until the mixture thickens.
If your mix is still too thin, you can add a cornstarch slurry at a 1:1 ratio. One tbs of cornstarch to 1 tbs water added to the soup and stir until thickened.
If your mix is too thick, you can add a little water or broth to desired consistency.