Preheat the oven to 400℉. On a large rimmed baking sheet, toss the mushrooms with 2 tablespoons of oil. Roast, tossing halfway through cooking, until golden brown and fragrant, about 15 minutes. Season with salt and pepper.

In a large skillet, heat 2 tablespoons of the oil. Add the shallots and season with salt and pepper. Cook over moderate heat, stirring occasionally, until translucent, about 8 minutes. Add the mushrooms to the pan with the shallots and heat through.

Deglaze the pan with the Marsala wine, scraping up any brown bits on the bottom of the pan, and cook until almost reduced. Add the beef stock, heavy cream, thyme and rosemary. Simmer until thickened and creamy, about 15 minutes. Discard the herb stems and season with salt and pepper.

Meanwhile, season the chicken breasts with salt and pepper. Dredge in the flour, shaking off the excess.

In a large nonstick skillet, heat ¼ cup of oil. Working in batches (be careful not to crowd the pan), cook the chicken breasts over moderate heat until golden brown and just cooked through, 3 to 5 minutes per side. Transfer the chicken to a paper towel-lined plate and season with salt. Repeat with the remaining chicken.

Transfer the chicken to a platter and spoon the mushroom sauce over the top. Garnish with chopped parsley and serve right away.