1. Add the potatoes, mushrooms (optional), carrots, and onion to the slow cooker.
2. Heat half the olive oil over medium high heat in a large pan. Coat cubed beef chuck in flour and add to the pan. Cook until the beef is browned on all sides. Using a slotted spoon, add the beef chuck to the slow cooker.
3. Reduce pan heat down to medium and add the rest of the oil and all of the flour to the pan.
4. Cook for about 1 minute and then add the tomato paste and spices. Stir to evenly combine and form a paste. Next, add the beef broth to the pan in intervals, 1/4 cup at a time, while stirring to form a thick gravy and avoiding lumps.
5. Once all of the broth has been incorporated, bring to a simmer and then remove from the heat. Add the gravy to the slow cooker and evenly coat the vegetables and beef.
6. Cook the stew in the slow cooker on low for 8 hours or on high for 4 hours. The stew is finished when the vegetables and beef are tender.