Heat the olive oil in a large pot over medium heat.
Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and ground ginger, cooking for an additional 1-2 minutes.
Mix in the pumpkin puree, cinnamon, salt, and pepper, combining well.
Pour in the broth and bring the mixture to a simmer.
Let the bisque simmer for about 20 minutes, stirring occasionally.
Use an immersion blender to puree the bisque until smooth.
Stir in the heavy cream and heat through without boiling.
Taste and adjust seasoning, adding more salt or pepper if needed.
Serve warm, garnished with fresh parsley or chives.