Melt the butter in a pan over medium heat, add the onions and mushrooms and cook until the mushrooms release their liquids and it’s absorbed, about 10 minutes.
Add the garlic and thyme and cook for a minute.
Add the wine and deglaze the pan.
Add the broth and cream, bring to a boil and simmer to thicken, about 2-4 minutes, before mixing in the cheeses and miso and removing from the heat.
Season with salt and pepper to taste.
