Saute celery and green onion in butter in a large saucepan until soft. Mix in flour, garlic, curry, salt, pepper and ginger. Add chicken broth, stirring until boiling and thickened.
Process with a hand blender (or in a regular blender) until smooth. Return to saucepan if you've used a regular blender. Stir in vegetable broth, pumpkin, peanut butter, yogurt, allspice and cayenne. Heat through before serving.