Preheat oven to 350 degrees.
Heat 2 tablespoons of olive oil in a Dutch oven (or a large, wide pot) over medium-high heat. Add mushrooms and cook for about 5 minutes, until moisture released by the mushrooms is reduced and mushrooms have started to brown.
Add celery and onion and cook, stirring, 5 minutes. Add dried herbs and garlic and cook for a minute more. Stir in butter, Kitchen Accomplice Veggie Broth Concentrate or Vegan Plant-Based No-Bone Broth Concentrate, and water and bring the mixture to a simmer. Turn off heat.
Gradually add croutons to the mixture in the pot, stirring gently. Stir in parsley and season to taste with salt and pepper. Drizzle with the remaining 2 tablespoons of olive oil and bake on the center rack of the oven 30 to 35 minutes, or until the mushroom stuffing is nicely browned and cooked through.