1
Heat the oil and butter in a large pan. Add the onion, garlic, carrots, celery and leeks and cook for 10 minutes until softened down. Season well.
2
Add the rest of the veggies and cook for a few minutes more, then pour in the stock. Season well and bring to the boil, then reduce to a simmer and cook gently for 20 minutes until the veggies are all tender, adding the peas for the last few minutes. Spoon out one-third of the veggies with a slotted spoon and set aside.
3
Blitz the rest of the soup with a stick blender until smooth, then remove from the heat. Stir in the reserved whole veggies.
4
To make the croutons, heat the oil and butter with the rosemary sprigs in a large pan. When hot, add the cubes of bread, toss well then cook for 5-6 minutes until golden and crisp on all sides. Season with sea salt.
5
Add the cream to the soup and a good grating of nutmeg and serve with the rosemary croutons.
7
Allow to cool completely. Once cool, transfer to a sturdy freezer bag or container and freeze for up to 6 months. Defrost slowly in a pan over a low heat.