1.Heat oil in a large heavy-based saucepan over medium heat.Cook sage, garlic and leek, stirring, for 3 minutes or until leek is soft. Add parsnip, celery and kale; cook, stirring, for a further 2 minutes or until kale is bright green. Add stock; bring to the boil. Reduce heat to low; cook for 15 minutes or until parsnip is almost tender.
2.Add green beans, zucchini and cannellini beans; cook for a further 5 minutes or until zucchini is just tender. Season.
3.Meanwhile, make pesto.
4.Serve soup topped with pesto.
Pesto
5.Blend or process ingredients until smooth. Transfer to a small bowl; season to taste.
Cut the leek in half lengthways and rinse carefully between the layers; they can be quite gritty. Soup can be made a day ahead. Pesto can be made 3 days ahead. Store in separate airtight containers in the fridge; cover pesto with a thin layer of oil. Soup and pesto can be frozen in separate airtight containers for up to 3 months. Serve minestrone with crusty bread, basil leaves and extra grated parmesan, if you like.