01 - Preheat oven to 325°F.
02 - Toss beef cubes with 2 tbsp flour, salt, and pepper until evenly coated.
03 - In a large Dutch oven or heavy pot, heat oil over medium-high heat. Brown the beef in batches, transferring browned meat to a plate.
04 - Add onion to the pot and cook until softened, about 4 minutes. Stir in garlic, cooking for 1 minute more.
05 - Return browned beef to the pot. Add carrots, parsnips, potatoes, and celery. Stir in tomato paste and cook for 2 minutes.
06 - Pour in beef stock and Guinness (if using). Add bay leaves, thyme, and rosemary. Bring to a simmer.
07 - Cover and transfer to the oven. Cook for 1½ hours.
08 - Meanwhile, prepare the dumplings: In a bowl, mix flour, baking powder, and salt. Rub in the butter until the mixture resembles coarse crumbs. Stir in parsley and chives. Add milk and mix gently until dough forms. Do not overmix.
09 - After 1½ hours, remove stew from oven. Discard bay leaves.
10 - Drop spoonfuls of dumpling dough (about 2 tbsp each) onto the surface of the simmering stew. Cover and return to the oven for 25–30 minutes, until dumplings are puffed and cooked through.
11 - Taste and adjust seasoning. Serve hot, garnished with extra parsley if desired.