Place the tomatoes and the jalapeño chillies on a baking sheet and put under a hot grill, let the skin go black, the flesh soft, then turn and blacken the other side, when coolish, roughly chop, removing the stems from the chillies and core from the tomatoes. Leave the blackened skin as this adds flavour and nice black specs to the finished sauce.
While the tomatoes and chillies are roasting. Heat a dry pan over medium heat, place the cloves of garlic and let them get soft, sweet and black in spots, turning as you go. Let cool and peel.
In a jug suitable for a stick blender, place all the ingredients except the salt, blitz until smooth, add salt to taste.
Use straight away or keep refrigerate up to 3 days. For best flavour bring to room temperature before using.