Preheat the oven to 180°C. In one saucepan get the stock to simmering point and add the green tops and the garlic while you get on with the rest. In a large casserole dish melt the butter, then fry the bacon over a medium heat until crisp and then remove. Make sure the leeks are washed and add to the pan, then pop the lid on and turn the heat down to low.

Meanwhile, bake the potato peelings. Toss the peelings in a little oil, salt and pepper and put on a baking tray in one layer. Pop in the oven for 10 - 15 minutes until crisp and then put aside to cool.

After 10 minutes the leeks should be softened so add the potato, crank up the heat and fry for a couple more minutes to warm up the potato. Fish the garlic out of the stock (it should be bobbing on top anyway) and add to the leeks and potatoes. Discard the green leek tops and add the stock to the pan. Bring to the boil then simmer for 15 minutes or until the potato is tender. Blitz a bit with a food processor until it's the texture you like (I like thick but not pureed, but hey-ho).

Ladle out the soup into bowls and top with the bacon and crispy potato skin.