Pat the beef chuck cubes dry with paper towels. Season generously with about ½ teaspoon of the kosher salt and ¼ teaspoon of the black pepper. This initial seasoning is crucial for building flavor.

Heat the olive oil in a large, heavy-bottomed skillet or Dutch oven over medium-high heat. Once the oil is shimmering, add half of the beef cubes to the hot pan in a single layer, being careful not to overcrowd. Sear the beef on all sides until deeply browned, about 2-3 minutes per side. This browning process (Maillard reaction) creates immense flavor. Remove the seared beef from the skillet and set aside on a plate. Repeat with the remaining beef, adding a little more oil if the pan seems dry.

Reduce the heat to medium. Add the chopped onion, carrots, and celery (the “soffritto”) to the same skillet. If there isn’t enough residual fat, add another teaspoon of olive oil. Sauté for 8-10 minutes, stirring occasionally, until the vegetables are softened and the onion is translucent. Add the minced garlic and optional red pepper flakes (if using) and cook for another 1-2 minutes until fragrant, being careful not to burn the garlic.

Stir in the tomato paste and cook for 2-3 minutes, stirring constantly. Cooking the tomato paste deepens its flavor and removes any raw taste.

Pour in the red wine to deglaze the pan. Scrape up any browned bits (fond) from the bottom of the skillet with a wooden spoon – these bits are packed with flavor. Let the wine simmer and reduce by about half, which should take 3-5 minutes. This cooks off the alcohol harshness and concentrates the wine’s fruity notes.

Transfer the sautéed vegetable mixture to the insert of your slow cooker (6-quart or larger recommended). Add the seared beef cubes on top of the vegetables.

Pour the crushed tomatoes, diced tomatoes (with their juice), and beef broth over the beef and vegetables. Add the bay leaves, dried oregano, dried thyme, and dried rosemary (or fresh sprig). Stir gently to combine everything.

Cover the slow cooker and cook on LOW for 6-8 hours or on HIGH for 3-4 hours. The beef should be incredibly tender and easily shreddable when done. The exact time will depend on your specific slow cooker model.

Once the cooking time is complete, carefully remove the beef chunks from the slow cooker and place them on a clean cutting board. Using two forks, shred the beef. It should fall apart easily. Discard any large pieces of fat or gristle that didn’t render down, and remove the bay leaves (and fresh rosemary sprig, if used) from the sauce.

Return the shredded beef to the slow cooker and stir it into the sauce. Taste the ragu and adjust seasonings as needed. Add the remaining ½ teaspoon kosher salt and ¼ teaspoon black pepper, or more, to your preference. If the sauce seems too thick, you can stir in a little more beef broth or some of the hot pasta water. If it’s too thin for your liking, you can remove the lid and cook on HIGH for another 20-30 minutes to allow it to reduce slightly, or make a small slurry of cornstarch and water to thicken it (though this is usually not necessary).

For the best flavor, turn off the slow cooker, cover, and let the ragu rest for at least 15-30 minutes before serving. This allows the flavors to meld even further.

Serve the hot beef ragu generously spooned over your favorite cooked pasta. Garnish with freshly grated Parmesan cheese and a sprinkle of chopped fresh basil or parsley.