Put ¼ cup (60 ml) of the water and the mushrooms, onion, and garlic in a medium saucepan. Cook over medium heat, stirring occasionally, until the vegetables are soft, about 10 minutes. Add more water if needed to prevent sticking.
Add the remaining 2¼ cups (550 ml) of the water and the nutritional yeast, tamari, miso, poultry seasoning, and pepper. Decrease the heat to low and cook, sti