01 - Heat olive oil or butter in a large pot over medium heat. Add sliced leeks and sauté for 5 to 7 minutes, stirring occasionally, until leeks are softened but not browned.
02 - Add diced potatoes and vegetable broth to the pot. Increase heat to bring to a boil, then reduce to a gentle simmer. Cook uncovered for 15 to 20 minutes, until potatoes are fork-tender.
03 - Remove the pot from heat. Using an immersion blender, blend the soup until completely smooth. Alternatively, work in batches with a countertop blender, returning soup to the pot after each batch.
04 - Stir in the heavy cream or plant-based cream. Season with salt and freshly ground black pepper to taste. Ladle soup into bowls and garnish generously with chopped chives.