Wash and thinly slice zucchini. In a large frying pan, melt butter. Add zucchini, onion and garlic and sauté 5 minutes. Add curry and simmer, covered, for 15 minutes. Blend mixture in blender until smooth. Add milk/cream and broth. Return to stove to warm. Serve with a dab of sour cream, or chopped cilantro or grated Parmesan cheese.