Preparation

1. Preheat the oven to 325°F, or set a slow cooker to low.
2. Pat the beef dry with paper towels.
3. Season the beef evenly with 2 teaspoons salt and 1 teaspoon black pepper.

Browning the Beef

1. Heat the oil in a large Dutch oven or heavy-bottomed pot over medium-high heat.
2. Add the beef in batches, browning on all sides.
3. Transfer each batch to a large bowl once browned.

Cooking the Aromatics

1. Add the onion and celery to the pot and cook until lightly browned, about 5 minutes.
2. Transfer to the bowl with the beef.
3. Add the garlic to the pot and cook for about 1 minute, stirring constantly.
4. Immediately add 1 cup of the water.
5. Increase heat to high and bring to a boil, scraping the bottom of the pot to release browned bits.
6. Cook until the liquid reduces by about half.
7. Stir in the tomato paste and cook for 1–2 minutes.

Building the Stew

1. Add the remaining 3 cups water and the beef base.
2. Reduce heat to medium-low.
3. Return the beef and vegetables to the pot.
4. Add potatoes, pearl onions, and mushrooms.
5. Stir to combine.

Thickening the Stew

1. In a small bowl, whisk together the flour and cold water until smooth.
2. Stir the mixture into the stew until fully incorporated.
3. Remove the pot from heat.

Oven Method

1. Cover the pot with a tight-fitting lid.
2. Place on the center rack of the oven.
3. Braise for 2 to 2½ hours, until the beef is fork-tender.

Slow Cooker Method (Beautiful 10-in-1 Electric Multi-Cooker)

1. Use the sauté function to brown the beef and vegetables as directed above.
2. Switch to slow cook mode on low.
3. Cover and cook for about 6 hours, until the beef is tender.

Finishing

1. Stir in the fresh thyme.
2. Taste and adjust seasoning with additional salt and pepper as needed.