While vegetables are cooking make the gravy: Finely chop the mushrooms.
Melt 5 Tablespoons butter in a medium saucepan over medium heat.
Add chopped mushrooms to the butter and cook for 5 minutes, until the mushrooms have released their liquid.
Add the flour and stir constantly, the mixture will become pasty, the flour may stick to the bottom of the pan, this is okay. Cook for about a minute.
Add the broth 1/4 cup at a time, stirring to release the bits from the bottom of the pan. Continue adding the broth while stirring constantly until all the broth is added. Bring the mixture to a boil then turn down to a low boil. Stir and boil for 5 minutes, until slightly thickened.
Once the vegetables are cooked add the thyme, salt and pepper and stir to combine.
Combine the cooked vegetables, cut up chicken, and gravy in one pan. Stir well and taste. Add more salt and pepper to your taste. Set aside to cool slightly.
Heat oven to 400°F.