Put potatoes, tomatoes, carrots and celery in the crockpot. Have the beef broth and cooking wine measured out and ready.
Heat a frying pan up on high. Add in 2 TBSP oil. Add garlic. Once pan is hot, add beef. Sear beef for about 2 minutes on each side. Transfer beef out of pan after 5 minutes.
Do not wash the pan! The technical term here is deglazing- we're going to add liquid that will help loosen up and remove the flavorful meat remnants on the bottom of the pan. Return pan to hot stove top and add remaining 2 TBSP of oil. Once oil is hot, add in the onions. Wait about 3-4 minutes until the onions are beginning to be translucent and are sizzling. Add in cooking wine and beef broth. Once the liquid begins to boil, turn off the heat and pour entire mixture into the crockpot.
Add spices and seasonings, mushrooms and bay leaf. Stir lightly to combine.
Cook on low for 9-10 hours, medium 7-8 hours, high 6-7 hours.
About 30 minutes prior to serving, ladle out about 1/2 cup of liquid from the stew. Whisk in 2 tsp cornstarch and add it back to the stew, stirring gently to combine. This helps thicken it up! If you want it even thicker, you can repeat this process once, waiting about 15 minutes between to double check thickness.