Add the beef, carrots, onion, garlic and beef broth to the slow cooker. Stir in the Worcestershire sauce and season with salt, pepper, garlic powder and onion powder.
Cover and cook on HIGH for about 6 hours, or until the beef is tender and the carrots are cooked through.
Stir in the frozen corn and peas.
Meanwhile, make the pumpkin dumplings. In a bowl, combine the flour, baking powder, salt, pepper, cinnamon and nutmeg. Add the pumpkin purée, milk and egg and stir just until a thick, sticky dough forms. Don't overmix.
Drop spoonfuls of dumpling dough over the surface of the hot stew. Cover and cook on HIGH for approximately 30 minutes, until the dumplings are puffed and cooked through.
Carefully remove enough dumplings to give yourself room to stir the stew without breaking them apart.
In a small bowl, whisk together the cornstarch and milk until completely smooth. Pour the slurry into the stew and gently stir it into the liquid. Return the dumplings to the top, cover, and cook for another 10 minutes, or until the broth has thickened into a creamy, rich gravy.
Taste and adjust the salt and pepper before serving.