Heat the olive oil in a Dutch oven over medium heat. Add the beef chunks and cook until browned on all sides, about 6 minutes.
Add the onion, carrots, and garlic to the pot. Cook for 4 minutes until the onion softens.
Sprinkle the flour over the mixture and stir for 1 minute to coat everything evenly.
Pour in the beef broth while stirring to avoid lumps. Add the sweet potatoes, nutmeg, salt, and pepper.
Bring the stew to a simmer, then cover and cook for 45 minutes until the beef and sweet potatoes are tender.
Use an immersion blender to partially puree about half the stew, leaving some chunks for texture.
Ladle into bowls and top each with a thyme sprig before serving.