Roast the jalapenos under the grill on a baking tray for 5-7 minutes per side until the skin is charred.
Place the garlic in a dry frying pan over medium heat, cook until browned in spots and soft, cool and peel. (we could use a little bit of raw garlic if you think better, not sure how Mexican this is)
De-stem the chillies and place them in a jug suitable for a stick blender. Add the peeled garlic and salt, blend until smooth, slowly add the oil so as to make an emulsion, when it is thick add the chopped coriander and pulse, so you get small flecks, then stir in the lime juice and cider vinegar, taste, it should be somewhat salty and tart, adjust if necessary. Scrape into a small bowl.