In a large pot or Dutch oven, heat the vegetable oil over medium-high heat. Add the beef cubes and brown on all sides, about 5-7 minutes. Remove the beef and set aside.
In the same pot, add the chopped onion and garlic. Sauté until the onion is translucent, about 3-4 minutes.
Return the beef to the pot and add the carrots, celery, beef broth, potatoes, thyme, rosemary, bay leaf, salt, and pepper. Bring to a boil, then reduce heat to low. Cover and let simmer for 1.5 to 2 hours, or until the beef is tender.
About 15 minutes before the stew is done, prepare the dumplings. In a mixing bowl, combine the flour, baking powder, salt, and pepper. Cut in the butter until the mixture resembles coarse crumbs. Stir in the milk until just combined.
Drop spoonfuls of the dumpling mixture onto the surface of the simmering stew. Cover the pot and cook for an additional 15 minutes without lifting the lid.
After 15 minutes, check the dumplings for doneness. They should be fluffy and cooked through. Stir in the frozen peas and let them heat through for a couple of minutes.
Remove the bay leaf before serving. Ladle the stew into bowls and enjoy!