Heat a skillet over high heat. Add 1 tablespoon olive oil. Season chuck roast with salt and pepper, then sear in the skillet for 3-4 minutes, until browned. Flip and repeat on the other side. If your slow cooker has a "Roast" or "Sauté" setting, you could use this.
Place the roast in the slow cooker, and sprinkle with the onion soup mix and the au jus mix. Pour the consommé and cream of mushroom soup over top and briefly mix together. Add in the mushrooms.
Cook on LOW for 6 hours.
Finely shred the chuck roast in the broth. Stir in the uncooked egg noodles. Recover and cook on HIGH for 1 hour.
Pour in the cream and mix thoroughly.
Scoop mashed potatoes onto a plate and top with a hearty helping of beef and noodles.