In a large pot, melt the butter over medium heat. Then, add the onions and garlic, and sautee, until onions are soft and translucent.
Add the pumpkin puree and broth, and bring to a boil. Then, reduce heat and simmer for 20 minutes.
Add the heavy cream (if using). Then, puree the soup. Use an immersion blender or a regular blender to do this.
Serve topped with a drizzle of cream, croutons, chopped bacon or pumpkin seeds, and a side of bread for dipping.