Step 1Heat oil in a large saucepan over a medium heat. Add onion, fennel and celery, and cook, stirring, for 6–7 minutes, or until softened. Add the garlic and oregano, and cook, stirring, for a further 1 minute, or until fragrant.
Step 2Add cannellini beans, potato and stock to pan with 2 cups of water, and bring to the boil. Reduce heat and simmer for 15 minutes, or until potato is tender. Add green beans zucchini and silverbeet, and cook for 5 minutes, or until vegies are tender. Season with pepper.
Step 3Divide soup among 4 serving bowls, top with a dollop of basil pesto and serve.