01 - Heat the vegetable oil in a large Dutch oven or heavy pot over medium-high heat. Brown the beef cubes in batches, seasoning with salt and pepper. Remove beef and set aside.
02 - In the same pot, add onion, garlic, carrots, parsnips, and celery. Sauté for 5 minutes until vegetables begin to soften.
03 - Stir in the tomato paste and cook for 1 minute. Sprinkle flour over the vegetables (if using) and stir to coat.
04 - Return the beef to the pot. Add beef stock, Guinness (if using), Worcestershire sauce, bay leaves, thyme, and rosemary. Bring to a simmer, scraping up any browned bits from the bottom.
05 - Cover and simmer gently over low heat for 1 hour 30 minutes, stirring occasionally.
06 - Meanwhile, prepare the dumplings: In a mixing bowl, combine flour, baking powder, and salt. Rub in the cold butter with fingertips until mixture resembles coarse crumbs. Stir in parsley and chives. Add milk and mix just until a soft dough forms. Divide dough into 12 equal pieces and shape into balls.
07 - After 1 hour 30 minutes, uncover the stew and discard bay leaves. Check seasoning and adjust with salt and pepper if needed.
08 - Place dumplings on top of the simmering stew. Cover and cook for 25 minutes without lifting the lid, until dumplings are puffed and cooked through.
09 - Serve hot, garnished with chopped parsley.