Sauté the leeks: In a large pot, melt butter over medium heat. Add the sliced leeks and cook for 5-7 minutes, stirring occasionally until softened. Be careful not to brown the leeks too much—this can make them bitter.
Add garlic: Toss in the minced garlic and cook for another minute, stirring so it doesn’t burn.
Simmer the potatoes: Add the diced potatoes and vegetable broth. Bring the mixture to a simmer and cook for about 25 minutes, or until the potatoes are tender.
Blend the soup: Once the potatoes are soft, use an immersion blender to purée the soup until smooth and creamy. If you prefer a chunkier texture, you can pulse for a few seconds instead.
Add cream and season: Stir in the heavy cream and season with salt and pepper to taste. Simmer for an additional 5 minutes to let the flavors meld together.
Serve: Ladle the soup into bowls and garnish with a sprinkle of fresh herbs, if desired. Serve hot and enjoy!