Combine all ingredients in small sauce pan, heat on medium, and whisk to keep from clumping... It's really easy and forgiving.
Notes
I tend to make it as an after thought and get busy with all the other pans on the stove. I've used it as a gravy, sauce and even as "cheese" in some dishes.
Substitutions
I've made it with rice, oat and wheat flour. I don't use soy sauce, but add salt. sometimes I put in some garlic or herbs too. I also tend to put MORE yeast in.
Omit soy sauce and add additional salt if avoiding soy.
Select a flour/thickener that is safe for your needs.
Nutritional yeast is better purchased pre-packaged than from the bulk bins to avoid cross contamination.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.