Place the stew meat, salt, pepper, and onion in the slow cooker. Stir to distribute the seasonings and onion.
In a small bowl, combine the garlic salt, Worcestershire sauce, beef broth and ketchup. Pour over the meat.
Cover and cook for 7-9 hours on low or 4-5 hours on high.
About 30 minutes before serving, combine the flour and apple juice in a small bowl, whisking vigorously to combine well.
Pour the flour mixture into the slow cooker, whisking quickly to mix in the roux with the stew meat and juices and to avoid lumps.
Add the mushrooms and stir.
Cook on high for 30 minutes.
Stir in 1/2 cup sour cream right before serving.
Serve over baked potatoes.
Notes
This also makes a great freezer meal! I store the leftovers in a freezer-safe container and then thaw in the refrigerator (usually takes about a day) and reheat over medium-low heat in a saucepan on the stove.How to make this in the Instant Pot:
Making this recipe in the Instant Pot is a little different! Push Saute on your Instant Pot and pour 1 Tablespoon of olive oil in. Put your meat on the bottom of the pan so you can mix it and sear it a little bit. (About 2 minutes)
Next add your garlic, mushroom, and onions and saute those also for 3 minutes.
Add 3 Tablespoons of flour into the beef mixture and stir until well combined
Add your Worcestershire sauce and beef broth (And ketchup and apple juice if you would like)
Put the lid on your Instant Pot and cook on Manual for 12 minutes.
Do a quick release, add 16 ounces of Egg Noodles into your pot and add another 1/2 cup of beef broth.
Close the lid and cook on Manual for 4 minutes. Do another quick release. Mix in 1/2 cup to 1 cup of sour cream and mix it in! If it is too runny, turn the saute button on and let it cook for a little longer!