In a Dutch oven, or other heavy liddes pot, heat the olive oil over low heat. Add the onions and garlic and saute for 5 minutes until the veggies soften. Add the mushrooms and a pinch of salt and saute for 10 minutes on low heat, stirring frequently.
Stir in the nutritional yeast, Dijon mustard, Herbes de Provance, garlic powder, onion powder, dried sage, and vegetable stock. Cover and simmer for about 20 minutes.
Whisk in the corn starch to the gravy, and stir for a few minutes until the gravy is thick. Taste and adjust seasoning.
Blend of desired for a smooth gravy.
Notes
*Note, feel free to adjust the salt to your preference. We tend to eat very low sodium, so this gravy is made with much less salt than normal. If you feel some is missing, add it in!