In a small pan, boil the balsamic vinegar on medium-high until reduced to 2 tablespoons, about 10 minutes.
Heat stock in a medium sauce pan, and keep at a simmer.
In a Dutch oven or large saucepan, heat ghee over medium heat. Add the mushrooms and saute until they are lightly browned and all of their liquid has evaporated. Remove from pan and set aside.
Heat 2 tablespoons of remain ghee or olive oil. Add leek, and cook until softened about 10 minutes. Add garlic and thyme and stir for one minute,
Add buckwheat and toast for about 1-2minutes. Add all of broth to risotto, reduce heat, cover and simmer until all of liquid is absorbed, about 10-15 minutes until buckwheat is al dente. Uncover and a ladel of water if pan is dry.
Turn off heat. Gently stir in mushrooms, parsley, and nutritional yeast. Drizzle a little fresh olive oil on top and serve.