Heat 1 teaspoon oil in a large Dutch oven over medium heat. Add leeks; sauté until tender, about 4 minutes. Stir in ginger and next 3 ingredients; cook 1 minute. Add water and next 3 ingredients. Bring to a boil; reduce heat, and simmer until pumpkin is tender, about 15 to 20 minutes. Stir in beans and next 3 ingredients; cook until beans are heated through, about 2 to 3 minutes.
Heat 2 teaspoons oil in a small saucepan over medium heat. Add pepitas, and sauté, stirring frequently, until lightly browned, about 2 to 3 minutes. Ladle stew into shallow bowls and top each serving with 1 tablespoon roasted pepitas.