Preheat the grill to high. Put the tomatoes, garlic and chillies in a grill pan without a rack and place under the hot grill. Turn frequently until the skins blister and start to blacken. The chillies will need about 5 minutes, the garlic 10 minutes and the tomatoes 15–20 minutes.
Peel the garlic and the chillies and remove the seeds from the chillies. Using a mortar and pestle, grind t