The main ingredient in Uttar Pradesh, Punjab, New Delhi, and other parts of northern India is khoa. It is a key ingredient in barfi and pedha, a round sweet flavored with chopped nuts and cardamom associated with the cities of Varanasi and Mathura. Petha, a famous dish of Agra, is a cross between fudge and preserves. Ash gourds are soaked in lime (calcium carbonate), boiled in alum powder and water, and then cooked again in sugar syrup. The result is a lovely, pale green, subtly flavored delicacy.