Pat meat dry with paper towels and season with salt and pepper on all sides. In large skillet heat 1 tablespoon oil over medium heat until just smoking. Cook half of beef until well browned all over, about 8 minutes. Transfer to slow-cooker insert and repeat with additional 1 tablespoon oil and remaining beef.
Add 1 tablespoon oil, onions, and ¼ teaspoon salt to now-empty skillet and cook until browned, 6-8 minutes. Add tomato paste and cook, stirring often, until paste begins to darken, about 2 minutes.
Stir in broth, soy sauce, Worcestershire Sauce, and bay leaves and bring to boil. Transfer to slow cooker.
In large bowl toss together carrots, parsnips, potatoes, remaining oil, ½ teaspoon thyme, ½ teaspoon salt, and ½ teaspoon pepper.
Place vegetables on one side of large piece of heavy-duty aluminum foil. Fold foil over vegetables to form packet that will fit in slow cooker; crimp edges to seal. Stir tapioca into slow cooker; set vegetable packet on top of beef.
COOK IN SLOW COOKER:
Cover and cook on high until beef is tender, 6-7 hours (or cook on low 10-11 hours). Remove bay leaves and place vegetable packet into large bowl. Carefully open packet and return vegetables and any accumulated juices to slow cooker.
Stir in remaining thyme and peas, cover, and let stand until heated through, about 5 minutes. Season with salt and pepper and serve.