Preheat oven to 400 degrees F.
Oil a baking sheet and place squash cut side down on sheet
Place pumpkin seeds in a small bowl and add oil. Mix to coat and spread seeds on baking sheet with squash.
Bake for 1 hour. After 15 minutes check to see if seeds are browned. When brown, remove from oven and set aside.
After 1 hour, remove squash from oven and let cool. Scoop pulp out and discard skin.
Heat a large pot over medium heat, adding butter. When melted, add leeks, ginger, squash and 4 cups of chicken stock. Simmer for 20 minutes.
Transfer to a food processor and puree until mixture is smooth.
Return soup to pot; add 2 cups chicken stock and remaining salt. Reheat and ladle into bowls.
Garnish with toasted pumpkin seeds.