Melt butter in stockpot, sweat leeks until tender.
Add potatoes and water/base powder to stockpot. Liquid should cover potatoes by 3". Bring to boil, lower heat to medium. Simmer 45 minutes or until potatoes are tended.
Add spices to soup. Simmer 10 minutes. Turn off heat, let cool.
Process to smooth, adding cream while processing.
Garnish with scallions or deep fried leeks.