Heat one tablespoon olive oil in skillet over medium heat. Add onions and apple pieces. Cook for about 5 minutes, until onions are softened and translucent. Add minced garlic and cook for an additional 30 seconds, until it is golden and fragrant.
Stir in vegetable broth, pumpkin puree, pumpkin pie spice, honey, salt, and curry powder. Allow to cook for 20 minutes over medium-low heat until barely simmering. Add additional stock or water if a thinner consistency is desired.
Puree in batches in a blender, filling halfway each time, or use an immersion (hand) blender to puree the soup directly in the pot. Top with sour cream or Greek yogurt and chopped nuts, if desired.