Preheat oven to 300°F with a rack in lower third position. Gather all ingredients.
Heat oil in a large (about 6-qt.) Dutch oven over medium-high. Sprinkle beef evenly with salt. Place beef in Dutch oven in a single layer, and cook, undisturbed, until deeply browned on 2 sides, 5 to 6 minutes per side. Transfer to a large plate; set aside. Do not wipe Dutch oven clean.
Add onion and celery to reserved Dutch oven; cook over medium, stirring often, until softened and translucent, about 6 minutes. Add garlic, tomato paste, and pepper; cook, stirring constantly, until tomato paste has darkened in color, about 2 minutes.
Stir in carrots, potatoes, broth, ranch dressing mix, Worcestershire, thyme, bay leaves, sugar, and reserved browned beef, along with any accumulated juices on plate, into onion mixture. Bring to a simmer over medium. Cover, and bake in preheated oven until beef is fork tender, 2 ½ to 3 hours.
Remove and discard thyme sprigs and bay leaves. Carefully transfer beef to a plate or cutting board and shred with 2 forks; return to Dutch oven. Garnish with parsley and serve with crusty bread.
