Heat a heavy-based pan over high heat, add the unpeeled garlic and roast for 15 minutes, turning halfway through, until the outside is blackened. Remove from heat, squeeze the garlic out of the skins and roughly chop.

Place whole tomatoes under an oven grill and cook until the skins are dark and blistered, then turn and cook the other side. Remove from the grill, allow to cool, then peel.

Place tomatoes and garlic in a food processor and blend. Add chillies, one at a time, and process to combine. Try the sauce as you go and add chillies to taste as one or two may be enough. Heat oil in a wide-based pan, add sauce and cook over medium heat to thicken. Add salt to season, if required. The sauce is now ready to be used or refrigerated for later.