Place the vegetable broth, onion powder, garlic powder, nutritional yeast, soy sauce, Dijon mustard, and flour in a medium saucepan. Whisk well to combine the flour with the liquid.
Bring the mixture to a boil over medium-high heat. Stir constantly as it simmers for 5-7 minutes until the gravy thickens.
Remove the saucepan from heat. Taste the gravy and adjust seasonings if needed. Serve warm and store any leftovers in the fridge.