Trim leeks, rinse to remove any sand, and thinly slice

Melt 3 tablespoons butter in a large skillet over medium heat and saute leeks for about 4 minutes

Add potatoes and broth and bring to a boil. Boil for 2 minutes then reduce heat and simmer until potatoes are cooked

Season to taste with cayenne, nutmeg, salt, and white pepper.

Transfer veg to blender and puree a little at a time

Add the cornstarch or flour and butter mix to thicken.

Serve right away or put the soup in the fridge till next day, reheat and enjoy.