In a medium saucepan, heat oil over medium heat. Add onion, celery, and salt, and cook, stirring, for about 5 minutes or until onions are translucent and celery is softened.
Add garlic and cook for another minute, stirring, until garlic is fragrant.
Add curry powder and cook for another minute, stirring, to toast spices.
Stir in broth and pumpkin and cook until simmering. Remove from heat and CAREFULLY blend using an immersion blender. Slowly stir in yogurt.
If needed, heat again over low heat to warm through.