Melt butter in large saucepan over medium high heat. Add onion and garlic; cook for 3-5 minutes or until tender. Stir in curry powder, salt, coriander and crushed red pepper; cook for 1 minute. Add water and bouillon; bring to a boil. Reduce heat to low; cook, stirring occasionally, for 15 to 20 minutes to develop flavors.
Stir in pumpkin and half-and-half; cook for 5 minutes or until heated through.
Transfer mixture to food processor or blender (in batches if necessary); cover. Blend until creamy. Serve warm or reheat to desired temperature. Garnish with dollop of sour cream and chives if desired.