Melt butter in a large pot over medium heat.

Add the leeks and sauté until softened.

Pour in chicken stock, white wine, and add the chopped sweet potatoes.

Bring the mixture to a boil.

Reduce the heat to low and simmer for 15 minutes, or until sweet potatoes are tender.

Stir in lime zest, lime juice, milk, and whipping cream.

Season with salt and pepper to taste.

Carefully puree the soup in small batches using a blender or immersion blender until smooth.

Transfer the pureed soup to a container and refrigerate for at least 4-6 hours to chill.

Serve cold, garnished with fresh chopped chives.