1 head garlic
3 tablespoons unsalted 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 (I used 5 cups; add the extra cup after pureeing if you’d like a thinner soup)
2 bay leaves
Table salt
2 1/2 pounds russet potatoes, peeled and cut into 1/2-inch cubes
1/3 cup sour cream
Ground black pepper

Toppings, optional:
Minced fresh chives or scallions
Bacon bits
Sour cream
Grated cheddar
A drizzle of melted (or melted and browned) butter