01 - Slice leeks in half lengthwise, rinse thoroughly to remove grit, then slice thinly.
02 - Melt butter in a large pot over medium heat. Add diced onion, sliced leeks, and minced garlic; sauté for 5 to 7 minutes until softened but not browned.
03 - Stir in diced potatoes, bay leaf, kosher salt, and black pepper until vegetables are evenly coated.
04 - Pour in vegetable stock, bring to a boil, then reduce heat and simmer covered for 20 minutes or until potatoes are very tender.
05 - Take out the bay leaf from the pot before blending.
06 - Use an immersion blender to purée the soup until smooth, or blend in batches using a countertop blender and return to pot.
07 - Stir in heavy cream, warm gently over low heat, and adjust seasoning as necessary.
08 - Ladle soup into bowls and garnish liberally with finely chopped fresh chives.