Add the bacon to a large heavy-bottomed soup pot over medium heat. Cook the bacon until the fat is rendered and the bacon is crispy, about 8 to 10 minutes. Use a slotted spoon to remove the bacon to a paper towel lined plate, reserving as much fat in the pan as possible.

Add the butter and allow to melt then add the onion and leeks. Sauté, cooking until the onion is soft and translucent, about 6 minutes. Add the garlic and cook until just fragrant, about 30 seconds. Add the potatoes, milk, chicken broth and 2 teaspoons of kosher salt.

Bring the soup to a boil over medium-high heat, then lower heat to medium-low and simmer until the potatoes are tender, about 20 minutes.

Puree the soup with an immersion blender until smooth or let the soup cool slightly then puree in a blender, working in batches if necessary.

Return the soup to the pot then stir in the sour cream and 1/2 cup of the cheese until combined. Season to taste with salt and pepper. Ladle the soup into bowls and top with sour cream, bacon, remaining cheese and chives.