01 - Preheat oven to 325°F.
02 - Toss beef cubes with 2 tbsp flour, salt, and pepper.
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.
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.