1Put the olive oil in a saucepan over medium heat and add 3.5oz of the pancetta, cooking until the pancetta is starting to color.
2Add the onion, celery and garlic, cooking until the onion is soft (approx 10 mins).
3Add the potato, chopped rosemary and stir well and cook for a further minute.
4Stir in the beans, milk and stock.
5Bring to the boil and then reduce to a simmer, until the potatoes are soft.
6While the soup is simmering, add a tbsp of oil and the remaining pancetta and cook until crispy, then set aside.
7Off the heat, use a stick blender to puree some or all of the soup, depending on whether you want a smoother or chunkier consistency.
8Serve the soup garnished with the fried pancetta, and a generous serving of bread and butter.