1 head garlic
3 tablespoons butter
2 medium leeks, white and light green parts halved lengthwise, washed, and chopped small
5 to 6 cups low-sodium chicken or vegetable broth
2 bay leaves
2 1/2 pounds russet potatoes, peeled and cut into 1/2-inch cubes
1/3 cup sour cream or yogurt
Ground black pepper
Rinse the head of garlic to remove any outside grit or dirt. Cut the top third off the head and peel any loose papery skins off the bottom two-thirds. Pop out the garlic clove tips from the top third and mince them.
In a large, heavy pot, melt the butter over medium heat. Add leeks and cook them until soft (but not brown), about 5 minutes. Add the minced garlic and cook another minute. Add the larger part of the garlic head (whole, not chopped), 5 cups broth, bay leaves and 1 teaspoon salt. Reduce heat and simmer for 5-10 minutes. Add potatoes and continue to simmer, partially covered, until potatoes are tender, about 20 minutes.
Discard bay leaves. Remove garlic heads. If you’d like an extra garlic boost to the soup, using tongs or paper towels, squeeze garlic head at root end until cloves slip out of their skins. Using a fork, mash the garlic cloves to smooth paste and add it back to the soup.
Add sour cream or yogurt to soup and cook for another 2 to 3 minutes. Adjust seasonings, adding more salt and pepper to taste. Using immersion blender, process soup until chunky-creamy, leaving lots of potato texture intact. Add up to 1 cup more broth for a thinner soup. Serve with oven-warmed crusty bread.