To a large saucepan, add the olive oil over medium heat.

Add the zucchini and a pinch of salt and pepper, sauté for about 3 minutes stirring occasionally. Add the shallot and sauté until softened. Add the garlic and cook for 1 minute being careful not to burn the garlic. Add the potato, bay leaf, cashews, stock, basil and another pinch of salt and pepper. Bring to a boil and simmer for 10 minutes until the zucchini is softened. Remove the bay leaf. If you have an immersion blender, blend the soup in the pan. If not transfer in batches to a blender. Add more stock if the soup is too thick. Taste for seasoning.

To make the basil oil:
Fill a large bowl with water and ice (this is to cool the basil quickly after blanching (boiling). Lay paper towels on a large plate or baking sheet (to drain the basil). Heat a deep sided skillet or large saucepan of water over high heat to boil and reduce to a low simmer. Add the basil leaves and blanch for 2 minutes, transfer to the iced water and leave for 1 minute. Take the basil out of the ice water and drain on the paper towels. Add the basil and oil to a food processor or blender. Blend until the mixture is fully pureed. Using a fine mesh sieve, strain the mixture into a jug.
Store in an airtight container in the refrigerator for up to 1 week.