Trim all visable fat from beef. Slice beef into 2 pieces.
Heat 1 Tbsp olive oil in a large heavy bottomed skillet over medium-high heat. Working with half of the beef at a time, dab both sides dry with paper towels, and season with pepper to taste.
Sear beef in skillet until browned, turning once halfway through, about 4 – 5 minutes total. Transfer beef to a plate to cool. When cool to the touch, slice the beef into bite sized cubes and place in the slow cooker.
Add remaining Tbsp oil in skillet, reduce heat to medium. Sauté onions and celery 3 minutes, add garlic, saute 30 seconds more, then add tomato paste and cook, stirring constantly, 1 minute.
Pour 1 cup beef broth into skillet along with Worcestershire, coconut aminos, thyme and rosemary. Add potatoes and carrots over beef layer in slow cooker, then pour broth mixture in skillet into slow cooker along with remaining 2 cups beef broth.
Cover and cook on low heat for 6-7 hours.
In a small bowl whisk together cornstarch with 1 ½ Tbsp cold water until smooth. Pour into slow cooker and gently stir, cover and cook on high heat for 20 – 30 minutes until thickened slightly.
Stir in peas and half of the parsley. Serve warm, garnished with remaining parsley.