To the slow cooker, add the onion, ginger, garlic, chicken, ground coriander, ground turmeric, garam masala, tomato paste, crushed tomatoes and tikka masala paste. Give it all a good stir to coat the chicken.
Set your slow cooker to low and let it work its magic for about 6–8 hours. Alternatively cook on high for 4 hours.
Just before serving, add the green beans and swirl in the greek yoghurt. Serve on brown or white rice.