– 5 pounds beef oxtails, trimmed
– 1 1/2 teaspoon kosher salt
– 1 teaspoon black pepper
– 1 tablespoon avocado oil or vegetable oil
– 1 medium onion, diced
– 1 green bell pepper, diced
– 1 red bell pepper, diced
– 2 celery stalks, chopped
– 4 garlic cloves, minced
– 1/4 cup all-purpose flour
– 4 cups beef broth
– 2 tablespoons Worcestershire sauce
– 2 teaspoon browning sauce (optional)
– 2 bay leaves
– 2 sprigs fresh thyme
– 1 tablespoon red wine vinegar (optional)