Heat oil in a large pot over medium heat & fry the onions for 20 minutes, stirring constantly to prevent burning. Add garlic & cook for 2 minutes. Add turmeric & pepper. Stir rapidly for a moment, then add the tomatoes & ginger. Cook for about 5 minutes (the fat should be separating from the gravy). Add tamarind & about 1 cup of the chick pea stock. Cover & simmer gently for 15 minutes. Add chick peas, garam masala & cumin. Cook for 10 minutes. Check for salt. Serve garnished with onion slices & shredded green chilies. Serve with Poori. Julie Sahni, "Classic Indian Cooking"