Start by preparing the pesto; placing the basil, pine nuts, extra-virgin olive oil, garlic and a little salt in a food processor. Blitz until smooth. Add the Parmesan and pulse until a thicker consistency is reached. Cover and chill until needed.
Heat the olive oil in a large saucepan over a moderate heat. Sauté the onion, garlic, carrot, celery and potato for 5-6 minutes, stirring occasionally, until softened. Add the tomato purée, vegetable stock and canned chopped tomatoes, stirring well to combine.
Bring to the boil, then reduce to a simmer for 10-15 minutes. Add the butter beans and macaroni, simmering for 10-12 minutes until the pasta and beans are soft. Adjust the seasoning and spoon into serving bowls.
Garnish with a basil leaf and a small tablespoon of the pesto. Serve with the sesame grissini on the side.