In a cast iron skillet over high heat, add 2 tablespoons of oil. Sauté mushrooms until browned, then transfer to the Crockpot.

Meanwhile, season the chuck roast with salt and pepper to taste. After transferring the mushrooms, add the remaining oil to the skillet and sear the roast on both sides until browned. Then transfer to the Crockpot.

In a bowl, whisk together the cream of mushroom soup, dry onion soup mix, and chicken stock. Pour over the roast in the slow cooker.

Cover and cook on low for 8-9 hours or on high for 3-4 hours. Once cooked, remove the roast from the Crockpot and stir the remaining sauce.

Serve the roast sliced topped with sauce from the Crockpot and garnish with fresh parsley.