1. Make the soup: melt butter over medium heat in a 24-quart stock pot. Add the leeks and garlic and cook, stirring regularly until soft, about 10 minutes. Do not brown.
2. Add the potatoes, stock, bay leaves, thyme, salt, and pepper and bring to a boil. Cover and turn down to low. Simmer for 15 minutes or until potatoes are soft. Remove thyme and bay leaf.
3. Make the cocktail potatoes, preheat fryer to 375°F, Toss the cooled, cooked mini potatoes in the beaten egg, coat with potato starch. Shake to remove excess and dip again in egg. Remove excess egg then toss in potato flakes until well coated.
4. Fry the coated marble potatoes for 1-2 minutes until golden and skewer 5 potatoes per skewer; keep warm until service.
5.Puree the soup with immersion blender until smooth; add heavy cream and bring back to simmer. If too thick, add more stock, if too thin, simmer longer to reduce.
6. Heat the whole milk to a simmer in a saucepot. Transfer to a blender and add the potato flakes and salt. Blend until frothy.
7. Just before serving, stir in the green onion puree, froth the potato milk and crisp the cocktail potatoes in a 375°F fryer.
8. Assemble the dish: garnish the soup with the potato froth, chives, and cocktail potatoes. Serve.