In a large pot or Dutch oven, melt the butter over medium heat. Add the diced onion and sauté for 5-7 minutes until soft and translucent.
Add the minced garlic and chopped sage, cooking for another minute until fragrant.
Stir in the pumpkin puree, broth, maple syrup, and nutmeg. Bring the mixture to a boil, then reduce heat and simmer for 15 minutes.
Using an immersion blender, puree the soup until silky smooth. Alternatively, carefully transfer to a regular blender in batches (be careful with hot liquids!).
Stir in the heavy cream and season generously with salt and pepper to taste. Let it simmer for another 5 minutes.
Serve hot, garnished with crispy sage leaves, a drizzle of cream, and toasted pepitas if desired.