In a large saucepan over medium heat, heat oil. Add onion, garlic, and silverbeet stems. Sauté, stirring, for 2 minutes until tender.
Pour in the stock and turn up the heat to medium-high. Bring it to a boil, then toss in the chicken and noodles. Stir until the noodles are loosened. Let it simmer without a lid for 8 minutes.
Combine corn and silverbeet leaves in the pot and cook for 3 to 4 minutes until corn is tender. Season with salt and pepper; then ladle the soup into warm bowls before serving.