Stir in tapioca starch to the mushrooms until dissolved. Add vegetable broth. Stir well and scrape up any brown bits at the bottom of the skillet. Simmer for 5-10 minutes.
Stir in coconut milk or dairy-free yogurt and simmer for another 2-3 minutes. Season with nutritional yeast, salt and pepper. Add spinach and cook until just wilted.