Bring the broth to boil in a pot, add sea salt.
Gradually whisk in the polenta flour, reduce the heat to low and cook for about 15 minutes or until mixture thickens and the polenta is cooked through. Stir frequently.
In a separate pan, while cooking the polenta, melt a third of the butter and add onion. Once the butter is absorbed, add a splash of white wine.
Once evaporated add your mushrooms (can leave them whole or chop them).
Add thyme, salt and pepper.
When the polenta is cooked add the remaining butter and cheese, stir well.
Serve a ladle of polenta with some mushroom sauce over the top.