Position the oven rack in the lower third part of the oven and preheat the oven to 325°F. Heat the olive oil over medium-high heat in a large dutch oven. Season the beef generously with kosher salt and black pepper and sear for 4-5 minutes on both sides, working in batches if necessary. Remove the beef from the pot.
¼ cup olive oil, 2 pounds chuck roast, 1 teaspoon kosher salt, 1 teaspoon black pepper
Reduce the heat to medium and add the mushrooms, onion, garlic, and fresh thyme to the pot. Sauté the vegetables for about 5-7 minutes or until softened and beginning to brown.
8 ounces button mushrooms, 1 large yellow onion, 4 cloves garlic, ½ tablespoon fresh thyme leaves
Add the beef and any juices back into the dutch oven along with ¼ cup of water. Scrape down the sides of the pot to prevent any of the vegetables from burning. Cover the dutch oven with the lid and place it inside the preheated oven. Cook for 1 ¼ to 1 ½ hours.
¼ cup + 1 cup water
Carefully remove the beef from the pot. Bring the beef drippings and vegetables to a simmer over medium-low heat. Once simmering, sprinkle in the flour to make a roux. Cook the roux, whisking occasionally, for 2-3 minutes. The roux should have a wet sand or paste-like consistency.
2 tablespoons all-purpose flour
Slowly drizzle in 1 cup of water, whisking continuously to prevent lumps from forming. Simmer until thickened. Taste for seasoning and add any additional salt and pepper as needed. Add the beef back into the pot and stir to coat.
Additional salt and pepper, ¼ cup + 1 cup water