Rachel Allen's Potato, Leek, and Smoked Bacon Soup

Heat the oil in a large saucepan over high heat, add the bacon, and sauté for about 1 minute, or until crisp and golden.

Remove from the pan and drain on paper towels.

Decrease the heat a little and add the butter to the oil in the pan. When it has melted, add the onion, leek, and potatoes. Season with salt and pepper and cook gently for 8 to 10 minutes without browning.

Pour in the stock and simmer gently for 5 minutes, or until the potatoes are completely cooked through.

Meanwhile, make the parsley pesto. Discard the stems from the parsley and put the leaves in a bowl with the garlic, pine nuts, Parmesan, and olive oil. Using a handheld blender, purée to a fairly smooth paste, adding a little more oil, if necessary, so that it is a thick but drizzling consistency. Alternatively, crush the parsley, garlic, and pine nuts using a mortar and pestle and stir in the Parmesan and olive oil. Season to taste with salt and pepper and set aside.

Purée the soup until smooth in a blender or using a handheld blender. Return to the pan and stir in all but 1 tablespoon of the reserved bacon pieces. Check the seasoning, adjusting if necessary, and heat for a minute more before serving.

Ladle the soup into warm bowls.

Drizzle over the parsley pesto and scatter the remaining bacon pieces on top.