In a large, heavy, oven-safe skillet over medium high heat, add 2 tablespoons of the olive oil and all of the mushrooms. Toss to coat and saute just until the mushrooms begin to brown and their moisture has released and evaporated.
Push the mushrooms to the side of the pan and add the remaining tablespoon of olive oil. Add the onion, celery and carrots to the oil and cook for a minute or two. Toss all of the vegetables in with the mushrooms and continue cooking until the onions begin to look translucent.
Add the flour and stir to coat all of the vegetables. Cook for about two minutes, then add the vegetable broth, stirring to combine. Add the peas, thyme, salt and pepper. Continue to cook for just a minute. Give it a taste and season accordingly.
Remove the skillet from the heat. Cover and allow to sit while you prepare the biscuits.
Preheat your oven to 375 degrees.