This comes straight from Chloe Coscarelli's Chloe's Vegan Italian Kitchen, where it accompanies the stuffed portobello mushrooms. I made a few minor adaptations.
1 tbsp olive oil
5 mushrooms, or stems of portobellos from other recipe
1/4 cup nutritional yeast
1/2 cup whole wheat flour
2 cups water
3 tablespoons Bragg's
2 garlic cloves
1 tbsp rosemary
salt and pepper
Heat olive oil in saucepan and saute onion and thinly chopped mushrooms. Add yeast and flour and whisk for 2 minutes. Add remaining ingredients and continue to whisk until very thick. Transfer to blender and puree until smooth.
And there's a bonus: if you make this with mushrooms it works wonderfully as a ravioli sauce. All you need to do is whisk the prepared gravy, or whatever's left of it, with an equal amount of cashew milk.