Preheat your oven to 400°F (200°C).
Place the pumpkin chunks on a baking sheet, drizzle with olive oil, and season with salt and pepper. Roast for about 30-35 minutes or until the pumpkin is tender and slightly caramelized.
In a large pot, heat the olive oil over medium heat. Add the chopped onion and garlic, sautéing until they become translucent and fragrant.
Stir in the cinnamon, nutmeg, and ginger, allowing the spices to bloom for a minute.
Add the roasted pumpkin to the pot and pour in the vegetable or chicken broth. Bring the mixture to a boil, then reduce the heat and simmer for about 15-20 minutes.
Use an immersion blender or a regular blender to puree the soup until smooth.
Return the soup to the pot and stir in the heavy cream or coconut milk. Warm the soup gently over low heat, being careful not to boil it. Season with salt and pepper to taste.
Ladle the creamy pumpkin soup into bowls, garnish with roasted pumpkin seeds and a drizzle of cream if desired, and serve hot.