Heat The Oil In A Large Heavy Pan Then Add The Chopped Onion And Stir For A Few Minutes With The Heat On High. Add The Cassia, Cardamons, Cloves And Fennel Seeds And Stir A Little Then Turn The Heat Down To Low And Cook For 10 Minutes. Add The Ginger And Garlic, Stir And Cook For Another 10 Minutes On Low Heat Stirring Now And Again To Make Sure Nothing Browns Or Burns. Add The Turmeric, Coriander And Chile Powder And Fry Gently For A Minute. Add 1 Tablespoon Of Yoghurt, Stir Round And Turn The Heat Up So The Yoghurt Sizzles In The Oil. When The Yoghurt Has Lost A Lot Of Its Moisture Add Another Tablespoon. Stir And Fry As Before. Repeat Until All The Yoghurt Is Incorporated. Add The Tomato Puree And Stir In.