MELT ghee or vegan butter in a medium pan over medium heat. Add finely chopped mushrooms and cook until tender, about 5-7 minutes.
WHISK together all other ingredients while mushrooms are cooking. Add to pan when mushrooms are cooked.
STIR the mixture continuously until it thickens, about 1-2 minutes. Don’t walk away from the pan or stop stirring to ensure an even consistency!
ONCE thick, remove from heat and either use for desired recipe or add to a sealed container. Soup will thicken even more as it cools.
REFRIGERATE for up to 1 week, if not using immediately, or freeze for up to 3 months. If frozen, thaw in the fridge overnight before using.