Pre-heat the BBQ for 2-3 minutes. Season the chicken generously with salt and coarsely ground pepper then add to the BBQ, cooking until golden, turning regularly, approx. 8 minutes per side. Remove from the heat and set aside for later.
Add the masala paste to the pan and cook for a minute until fragrant then add the tomatoes and simmer on a low heat for about 10 minutes until starting to thicken and reduced. Add the chicken back to the pan and cook for a further 8-10 minutes r until the chicken is cooked through. Turn off the BBQ and then add the yoghurt (or cream) and stir well to combine.
Serve immediately with rice or naans.