Method

1. Slice each leek lengthways, wash each half very thoroughly under running water to get rid of any hidden dirt. Finely slice the leeks.

2. Add olive oil to a large pot and heat on medium heat. Add the leeks, garlic and rosemary, and cook, stirring often, for 10 minutes, until everything is softened.

3. Add the stock, bring to the boil, then add the beans and simmer for 10 minutes.

4. Turn off the heat, then add the spinach and stir through just to wilt the leaves.

5. Serve the soup in bowls with a squeeze of fresh lemon juice.