Remove the ends and dark green tops of the leeks so you are left with just the light green and white parts. Cut each leek in half vertically.Thinly slice the leeks and place them in a large bowl.
Fill the bowl with water so that the leeks are now floating. Use your hands to rinse the leeks (the dirt will fall to the bottom of the bowl). Remove the leeks to a paper towel-lined bowl and dry them.
Add the bacon to a large pot over medium-high heat and cooked until crispy. Remove the bacon from the pot to a paper towel-lined plate to drain.
Reduce the heat to medium and add your leeks. Cook for 8 to 10 minutes until they are slightly wilted and soft. Do not brown the leeks.
Add the potatoes, chicken stock, salt, pepper, and bay leaf. Stir to combine.
Cover the pot and bring the soup to a boil. Reduce the heat to medium-low and simmer for 15 minutes.
Remove the bay leaf from the soup. Puree the soup using an immersion blender until smooth. (You can also puree the soup in a blender. Be very careful!! I do not recommend filling the blender more than halfway full = work in batches. Return the soup to the pot.)
Add the whipping cream, lemon juice, and nutmeg; stir to combine.
Bring the soup to a simmer and cook for 15 minutes, stirring often, until the soup thickens slightly.
Roughly chop the bacon and add it to your soup. Serve warm with a few chives sprinkled on top and a dollop of sour cream if desired.
If you prefer not to have bacon in your soup, use 2 tablespoon vegetable oil to cook the leeks instead of the bacon fat.