01 - Melt the butter in a large saucepan over medium heat. Add the leeks, onion, and garlic. Cook gently for 6 to 8 minutes until softened but not browned, stirring occasionally.
02 - Add the diced potatoes and bay leaf to the saucepan. Stir well to coat the vegetables with the buttery mixture.
03 - Pour in the vegetable stock and bring to a gentle boil. Reduce heat to low and simmer uncovered for 20 minutes, or until the potatoes are very tender and easily pierced with a fork.
04 - Remove and discard the bay leaf. Use a stick blender to purée the soup until smooth and creamy, or leave slightly chunky if you prefer more texture.
05 - Stir in the heavy cream until fully incorporated. Season generously with salt and freshly ground black pepper to taste.
06 - Reheat the soup gently over low heat if needed, taking care not to boil after the cream has been added to prevent separation.
07 - Ladle the hot soup into individual bowls and garnish with chopped fresh chives or parsley if desired. Serve immediately with warm crusty bread.