3 tablespoons unsalted butter
1 medium leek, white and light green parts only, halved lengthwise and chopped small (about 1 cup)
3 medium cloves garlic, minced or pressed through a garlic press (about 1 tablespoon)
2 heads garlic, rinsed, papery skins removed and top third of heads cut off and discarded
6-7 cups low-sodium chicken or vegetable broth
2 bay leaves
¾ teaspoon salt
1½ pounds russet potatoes, peeled and cut into ½-inch cubes (about 4½ cups)
1 pound red bliss potatoes (unpeeled), cut into ½-inch cubes (about 3 cups)
½ cup heavy cream
1½ teaspoons minced fresh thyme leaves
salt and freshly ground black pepper, to taste
¼ cup minced fresh chives
For the garlic chips:
3 tablespoons olive oil
6 medium cloves garlic, thinly sliced lengthwise
In a Dutch oven set over medium heat, melt the butter. Once foaming subsides, add leeks and cook until soft but not browned, 5-8 minutes. Stir in garlic and cook until fragrant, about 1 minute. Add garlic heads, 6 cups of broth, bay leaves and salt.
Partially cover pot and increase heat to medium-high. When mixture reaches a simmer, reduce heat and continue simmering 30-40 minutes or until garlic is soft enough to be easily pierced with the tip of a knife. Add potatoes and continue to simmer, partially covered, for 15-20 minutes or until potatoes are tender.
Meanwhile, make garlic chips by heating oil and garlic in a 10-inch skillet set over medium-high heat. Cook, turning frequently, until garlic is light golden brown, about 3 minutes. Using a slotted spoon, transfer garlic to a paper towel lined plate and sprinkle lightly with salt. Set aside.
Discard bay leaves and remove garlic heads from soup. Using tongs, gently squeeze garlic heads at the base to remove each clove from its papery skin. Using a fork, mash cloves to form a smooth paste.
Stir cream, thyme and half the garlic paste into the soup. Cook for about 2 minutes, until soup is warmed through. Taste and add additional garlic paste, if desired.
Using an immersion blender, carefully process soup until creamy but with some chunks remaining. Alternately, a potato masher can be used to mash some of the potatoes, but the consistency will not be as creamy. Add more broth if necessary to reach desired consistency. Add salt and pepper to taste. Serve soup with garlic chips and chives.