Using a stick blender or a high-speed blender, blitz the chillies, garlic and oil to a fine puree. Put a small, nonstick saucepan on a medium heat, add the chilli-garlic mixture and stir-fry for 10 minutes; if it starts to splutter too much, turn down the heat a little. Add the tomato puree, salt, sugar and 80ml water, stir-fry for two minutes, just to dissolve everything, then take off the heat and leave to cool. Once cool, decant into a sterilised jar, seal and store in the fridge.