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