Generously grease or line your crockpot with a crockpot liner. You'll need a large crockpot for this meal; I use a 6-quart.
Add in the uncooked meat (if you use beef stew meat or sirloin tip steak -- cut it against the grain into 1 inch cubes), gravy mix, dried onion flakes, all the seasonings, boullion granules, 2 and 1/2 cups beef stock (reserve the last 1/2 cup for later), minced garlic and mushrooms (add mushrooms halfway through the cooking time if you want them to be firmer).
Stir together and cover. Cook on low for 6-9 hours or until the meat is tender. Stir occasionally if you're around.
Once the meat is cooked through and tender, prepare the roux.
In a small saucepan over medium heat add in the butter. Melt.
Briskly whisk in the white flour and then cook for 1 minute.
Add in the reserved 1/2 cup beef stock or broth and whisk until smooth. Whisk in the half and half and briskly whisk until smooth.
Pour the roux into the crockpot (be careful it can sizzle and steam when added) and briskly stir to combine.
Follow package directions to cook the egg noddles and serve over the prepared egg noodles. Optionally garnish with a spoonful of sour cream (stir it in) and fresh parsley if desired. Season to taste with salt and pepper if desired.
*If you use beef chuck roast put all of the meat in the crockpot (no need to cook first or cut) with all the other ingredients and cook on low for 9-11 hours. Shred the meat when finished.