Step 1

Slice leeks into ¼-inch thick slices. Rinse under running water to remove dirt and sediment. Drain. ( The water will help soften the leeks as well.)

Step 2

Heat oil in a heavy-bottom pot or dutch oven, over medium-low heat. Add rinsed leeks and garlic and thyme, sauté until tender, golden and fragrant, 8-10 minutes.

Step 3

Add potatoes, stock, salt, and pepper. Bring to a boil, cover, turn heat to low and simmer, covered,  for 15-20 minutes, until potatoes are fork-tender.

Step 4

Make the optional leek oil.

Step 5

When the potatoes are very tender, use an immersion blender and blend the soup until relatively smooth. TIP: Over blending may cause the soup to have a gummy texture.  Alternatively, blend in batches in a regular blender (remember, you don’t want to fill up a blender with hot liquid, or you will have a soup explosion- so blend in small batches, less than half full,  holding the lid down firmly covered with a kitchen towel. )

Step 6

Return the blended soup to the pot, and whisk in the sour cream. Taste and adjust salt and pepper. Gently warm over low heat.

Step 7

To serve, divide among bowls, drizzle with the leek oil, sprinkle with fresh chives or scallions.