Sear beef: Pat dry, season, and brown beef in 1 tbsp oil until deeply caramelized. Remove to a plate.
Cook vegetables: Add remaining oil. Sauté onions, carrots, celery, parsnips, and mushrooms until softened and golden. Add garlic, cook for 1 minute.
Simmer: Return beef into the pot. Add in Guinness, add water (or broth). Season with tomato paste, thyme, bay leaves, fish sauce and soy sauce. Bring to a boil, cover and let it simmer gently for 1½ - 2 hours,
Add potatoes: Stir in potatoes, cook for another 30 minutes until tender and beef is soft.
Finish with peas: Stir in peas during the last 5 minutes (they should stay bright green).
Serve: Remove thyme and bay leaves. Taste, adjust seasoning, garnish with parsley.