Finely dice the onion, celery, and carrot so they are about equal sized pieces.
To an oven-safe pan, add the onion, celery, and carrot with 1 tbsp of neutral oil and cook until the onion is translucent.
Mince the garlic and add to the pan. Cook until fragrant.
Remove the stems from the mushrooms and cut the caps into thin slices. Add to the pan and cook until the mushrooms have shrunk and released their liquid.
Add the broth as well as the parley, basil, thyme, chicken-less seasoning, and bay leaf. Add the white wine and bring to a simmer.
Add the 1 tbsp of flour and whisk to remove chunks. Stir until the flour is Incorporated and cook until the mixture begins to thicken.
Once the mixture is thickened, remove from heat.